SEMICONDUCTOR DEVICE MANUFACTURING METHOD

Abstract: In a photoelectric conversion device manufacturing meth­ od which includes at least a step of forming a non-single-crystal semiconductor layer, a transparent or nontransparent layer, or a laminate member composed of transparent and nontranspar­ ent layers by patterning with a laser beam, a laser beam which has a short wavelength of 600 nm or less, a spot diameter of 3 to 60 nm and a width of 50 nano-second is used for the pat­ terning.

Description: Field of the Invention The present invention relates to a method for the manufacture of a semiconductor device such as a semiconductor photoelectric conversion device for example, and more particularly to an improved manufacturing method which includes at least one step of patterning a layer of the device with a laser beam. Description of the Prior Art Heretofore there has been proposed a semiconductor device manufacturing method which includes at least one step of patterning a non-single-crystal semiconductor layer, a transparent or non-transparent conductive layer, or a laminate member composed of transparent and non-transparent conductive layers, by irradiation with a laser beam. Compared with another manufacturing method which employs photolithography for the formation of such a patterned layer, the abovesaid laser beam irradiation method excels in that the patterned layer can be formed without any defects. The reason for this is that in the case of forming the layer by photolithography, a photoresist mask therefore is prone to pinholing or exfoliation at its marginal edges, which results in the formation of defects, whereas the method utilizing the patterning process with a laser bean has no such factors which cause defects. With the conventional method employing patterning with a laser beam as described for example in US-A-4 292 092 it has generally been the practice to use a YAG laser which emits a laser beam having a relatively long wavelength of about 1060 nm. However, the absorption coefficient of the abovesaid layers for a laser beam of such relatively long wavelength is extremely low. For example, the absorption coefficient of a non-single-crystal silicon layer is 10³/cm or so. In consequence, the laser beam tends to enter very deeply into the non-single-crystal semiconductor layer, transparent or non-transparent conductive layer, or laminate member. For instance, the penetration depth of such a laser beam into a non-single-crystal semiconductor layer is approximately 10 µm at a depth where the light intensity is 1/e (where e is nearly equal to 2.72) of the light intensity on the surface of the layer, and around 1000 µm at a depth where the light intensity is 1/100 of the light intensity on the layer surface. Accordingly, when a non-single-crystal semiconductor layer, a transparent or non-transparent conductive layer, or a laminate member as aforesaid is as thin as 1 µm or less, there is a substantial risk that a substrate or other layers underlying the layer to be patterned may be damaged if irradiation with a laser is utilized. Also there is a risk that the marginal edges of a non-single-crystal semiconductor layer, transparent or non-transparent conductive layer, or laminate member may be swollen or exfoliated if laser beam irradiation is utilized. Furthermore, in the case of a laser beam having such a relatively long wavelength of 1060 nm or so, it is difficult to reduce its minimum spot diameter to a small value of 100 µm or less. Therefore, it is difficult, with the conventional manufacturing method, to finely pattern the non-single-crystal semiconductor layer, transparent or non-transparent conductive layer, or laminate member with high precision. In addition, in the case of simultaneously forming a plurality of non-single-crystal semiconductor layers, transparent or non-transparent conductive layers, or laminate members, they cannot be spaced apart a small distance of 100 µm or less. This imposes severe limitations on the fabrication of a small and compact semiconductor device having a plurality of non-single-crystal semiconductor layers, transparent or non-transparent conductive layers, or laminate members. SUMMARY OF THE INVENTION According to the present invention therefore there is provided a method for the manufacture of a semiconductor device which includes a patterned transparent conductive film of not more than one micron thickness formed on a glass substrate, said film comprising indium oxide, said method including the patterning of the conductive film by irradiation of the same with a laser beam so as selectively to remove predetermined portions of the film, as known for example from US-A-4,292,092 abovementioned, characterized in accordance with the invention in that the laser which is utilized is a pulsed Excimer laser having a wavelength of 600nm or less and a pulse width of 50 nano-seconds or less and the mode of utilization of the laser is such as to effect removal of the film by sublimation without substantially affecting the underlying glass surface. The present invention also provides a method as defined above wherein a non-single-crystal semiconductor layer is formed on said transparent conductive film and said semiconductor layer is patterned by irradiation of the same with a laser beam having a wavelength of 600nm or less so as selectively to remove predetermined portions of the semiconductor layer and additionally wherein a non-transparent conductive layer is formed on said semiconductor layer and said non-transparent conductive layer is patterned by irradiation of the same with a laser beam having a wavelength of 600nm or less so as selectively to remove predetermined portions of the non-transparent conductive layer. The manufacturing method of the present invention thus differs principally from the conventional method above described in using, for the patterning of the respective layers, an Excimer laser beam having a wavelength of 600 nm or less which is far shorter than the wavelength of the beam employed in the conventional method. With the use of a pulsed Excimer laser beam having such a short wavelength equal to or less than 600 nm, the absorption coefficient of a non-single-crystal semiconductor layer, a transparent or non-transparent conductive layer, or a laminate member as abovementioned for the laser beam is far higher than the absorption coefficient for a YAG laser beam having a long wavelength of about 1060 nm. For example, the absorption coefficient of a non-single-crystal semiconductor layer is 10⁵/cm or more, which is more than 100 times larger than the absorption coefficient (approximately 10³/cm) for the laser beam of the 1060 nm or so wavelength used in the past. Therefore, the penetration depth of the laser beam of such a short wavelength into the abovesaid layer is far smaller than in the case of the laser beam of the above-mentioned long wavelength. For instance, the penetration depth of the laser beam of the 600 nm or less wavelength into the non-single-crystal semiconductor layer is 700 Å or less at a depth where the beam intensity is 1/e (where e is equal to 2.72) of the beam intensity on the layer surface, and 1 µm or less at a depth where the beam intensity is 1/100 of that on the layer surface. This is more than 1000 times smaller than the depth (10 µm or so) in the case of using the laser beam having the 1060 nm or so wavelength in the prior art manufacturing method. Therefore, according to the semiconductor device manufacturing method of the present invention, even if the non-single-crystal semiconductor layer, transparent or non-transparent conductive layer, or laminate member to be patterned is as thin as 1 µm or less, there is no possibility of damaging or patterning the underlying substrate or other layers by the Excimer laser beam. Further, the method of the present invention is free from the fear of swelling or exfoliating the marginal edges of the layer as a result of the patterning thereof. Moreover, the Excimer laser beam of the 600 nm or less wavelength can be easily reduced to such a minimum spot diameter as small as 100 µm or less. This permits the formation of the non-single-crystal semiconductor layer, transparent or non-transparent conductive layer, or laminate member with higher precision and more finely than in the past. Moreover, in the case of forming a plurality of such non-single-crystal semiconductor layers, transparent or non-transparent conductive layers, or laminate members, they can be spaced apart such a small distance as 100 µm or less. Accordingly, the manufacturing method of the present invention enables the provision of a smaller or more compact semiconductor device having a plurality of non-single-crystal semiconductor layers, transparent or non-transparent conductive layers, or laminate member than does the conventional method. It is per se known from the article "Industry-Compatible Applications for Visible Laser Energy in Semiconductor Production" by Richardson and Boogaard which appeared in Solid State Technology, Vol 25 (1982.03), pages 102-104, to utilize a YAG laser in a second harmonic mode wherein the laser beam wavelength was 532 nm. However this article discloses the use of such a laser beam only for mask making and in the fabrication of ohmic contacts, and contains no disclosure of the use of an Excimer laser in a method according to the present invention. Other features of the present invention are set forth in the appended claims and, together with the features discussed above, will become more fully apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1A to H are schematic sectional views illustrating, by way of example, a sequence of steps involved in the manufacture of a semiconductor photoelectric conversion device having a plurality of semiconductor photoelectric conversion transducers according to the present invention; Figs. 2A to D are schematic sectional views explanatory of a conductive layer which is formed on a substrate in the fabrication of the semiconductor photoelectric conversion device; Figs. 3A and B are schematic sectional views explanatory of a non-single-crystal semiconductor layer which is formed on the conductive layer in the fabrication of the semiconductor photoelectric conversion device; and Figs. 4A to C are schematic sectional views explanatory of a conductive layer which is formed on the non-single-crystal semiconductor layer in the fabrication of the semiconductor photoelectric conversion device. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to Fig. 1, the manufacture of the semiconductor photoelectric conversion device according to the present invention starts with the preparation of a transparent glass substrate 1 (Fig. 1A) having a surface 2. A transparent conductive layer 3 is then formed on the substrate 1, by means of a known evaporation method or CVD method (Fig. 1B). The transparent conductive layer 3 has a thickness of 1 µm or less and is constituted principally of a sublimable Indium oxide such as IN₂0₃ or ITO (Indium-Tin oxide). Next, the conductive layer 3 is subjected to patterning by the use of a laser beam, forming a plurality of conductive layers 5 which are each isolated from adjacent ones of them by a groove 4 of a width substantially equal to the spot diameter of the laser beam (Fig. 1C). The laser beam used in this case is a pulsed laser beam that has a short wavelength of 600 nm or less, a spot diameter of 3 to 60 µm and width of 50 nanosecond or less. As the pulsed laser beam, an Excimer laser operating at a wavelength of 193 nm or so (ArF), 248 nm or so (KrF), 308 nm or so (XeCl) or 315 nm or so (XeF) is employed. Since the laser beam has such a short wavelength of 600 nm or less, the absorption coefficient of the conductive layer 3 for the laser beam is more than 100 times larger than the absorption coefficient for a laser beam having a long wavelength of about 1060 nm which is obtainable with a YAG laser. Accordingly, the conductive layer 3 is effectively heated by the laser bean locally at the position of its irradiation. On the other hand, since the conductive layer 3 is as thin as 1 µm or less, it does not unnecessarily transfer therethrough heat resulting from the irradiation by the laser beam, namely the heat generated in the layer 3 does not unnecessarily escape therefrom to outside through the layer 3 itself. Moreover, since the substrate 1 is itself thermally insulating, hence it also prevents that the heat generated in the conductive layer 3 unnecessarily escape therefrom to the outside through the substrate 1. Accordingly, the material of the conductive layer 3 is effectively sublimed at the position of irradiation by the laser beam. As a result of this, conductive layers 5 are neatly formed, along with the grooves 4, as shown in Fig. 2A. In this case, there are no possibilities that the material of the conductive layers 5, molten by the laser beam irradiation, is deposited on the marginal edges of the conductive layers 5, as indicated by 6, in Fig. 2B. Further, since the laser beam is effectively absorbed by the conductive layer 3 because of its short wavelength, it would not inflict on the substrate unnecessary damages such as depressions and cracks as indicated by 7 and 8 in Figs. 2C and D. The effects described just above are prominent in the prior art when the conductive layer 3 is transparent. Next, a non-single-crystal semiconductor layer 11 is formed, by a known CVD, low-pressure CVD, plasma CVD or optical CVD method, on the substrate 1 so that it covers the conductive layers 5 and extend into the grooves 4 (Fig. 1D). The non-single-crystal semiconductor layer 11 also has a thickness of 1 µm or less. The non-single-crystal semiconductor layer 11 has such a PN junction structure that P-type non-single-crystal semiconductor layer and N-type non-single-crystal semiconductor layer are laminated one on the other in this order or in the reverse order, or such a PIN junction structure that a P-, I- and N-type non-single-crystal semiconductor layers are laminated one on another in this order or in the reverse order. The non-single-crystal semiconductive layer 11 is constituted mainly of a sublimable semiconductor such as Si, Si x Ge₁₋₄ (where 0 < x < 0.5), Si x C 1-x (where 0 < x < 1), Si₃N n-x (where 0 < x < 2) or Si0 2-x (where 0 < x < 1), and the layer 11 has introduced therein hydrogen or a halogen as a dangling bond neutralizer. Next, the non-single-crystal semiconductor layer 11 is subjected to patterning by a laser beam, forming a plurality of non-single-crystal semiconductor layers 13 each isolated from adjacent ones of them by a groove 12 of a width nearly equal to the spot diameter of the laser beam (Fig. 1E). In this case, the grooves 12 are each formed to expose each conductive layer 5 in the vicinity of each groove 4. Accordingly, each non-single-crystal semiconductor layer 13 extends on one conductive layer 5 and into the groove 4 and further onto the adjoining conductive layer 5 slightly. The patterning of the non-single-crystal semiconductor layer 11 may be effected by using the same laser beam as that for the formation of the conductive layers 5. Alternatively it may be effected by use of a YAG laser operating at 530 nm wavelength, or by use of a laser beam of a 514.5 nm or so, 488 nm or so, 458 nm or so, 363 nm or so or 351 nm or so wavelength which is obtainable from an argon laser, or a laser beam of a 337 nm or so wavelength which is obtainable with a nitrogen laser. The absorption coefficient of the non-single-crystal semiconductor layer 11 for the laser beam is also large as is the case with the aforementioned conductive layer 3, because the laser beam used has such a short wavelength as 600 nm or less. Therefore, the non-single-crystal semiconductor layer 11 is effectively heated at the position of irradiation by the laser beam as in the case of the aforementioned conductive layer 3. Further, since the non-single-crystal semiconductor layer 11 is at thin as 1 µm or less, it does not transfer laterally therethrough the heat generated therein preventing that the heat unnecessarily escapes from the layer 11 to the outside, as described previously. Moreover, the non-single-crystal semiconductor layer 11 is constituted principally of the sublimable semiconductor, as referred to previously. This enables the non-single-crystal semiconductor layers 13 to be formed neatly, along with the grooves 12 , as shown in Fig. 3A, and ensures to prevent that the material of each non-single-crystal semiconductor layer 13, molten by the laser beam irradiation, is deposited on its marginal edge, as indicated by 14 in Fig. 3B, and that the conductive layer 5 is hollowed, by the laser beam, to form therein a deep depression which may sometimes reach the substrate 1, as indicated by 15 in Fig. 3B. Next, a non-transparent conductive layer 21, which covers the non-single-crystal semiconductor layers 13 and extends into the grooves 12, is formed on the substrate 1 by the same method as that for the formation of the conductive layer 3 (Fig. 1F). The conductive layer 21 also has a thickness of 1 µm or less, and may be formed principally of a sublimable metal such as Cr, a Cr-Cu alloy (containing 0.1 to 50 wt% of Cu), Cr-Ag alloy (containing 0.1 to 50 wt% of Ag) or Cr-N alloy (containing 0.1 to 50 wt% of N), or a non-sublimable metal such as Al, Cu or Ag. Moreover, the conductive layer 21 may also be formed as a laminate member composed of a transparent conductive layer which may be constituted mainly of a sublimable metallic oxide such as Sn0₂, In₂0₃ or ITO or a sublimable metallic non-oxide such as Si-Cr or Si-Ni alloy and a non-transparent conductive layer which may be constituted mainly of the aforementioned sublimable or non-sublimable metal. In this case, the transparent conductive layer is formed on the side of the non-single-crystal semiconductor layer 13. Next, the conductive layer 21 is subjected to patterning with a laser beam, forming a plurality of conductive layers 23 which are each isolated from adjacent ones of them by a groove 22 of a width nearly equal to the spot diameter of the laser beam (Fig. 1G). In this case, the grooves 22 are each formed to expose one of the non-single-crystal semiconductor layers 13 in the vicinity of one of the grooves 12. Accordingly, each conductive layer 23 extends on one of the non-single-crystal semiconductor layers 13 and down into one of the grooves 12, wherein it is connected to the underlying conductive layer 5, and it further extends slightly onto the adjoining non-single-crystal semiconductor layer 13. The laser beam used for the patterning of the conductive layer 21 into the conductive layers 23 may be the same as that for the formation of the conductive layers 5 and the non-single-crystal semiconductor layer 13. Therefore, no detailed description will be repeated. The absorption coefficient of the conductive layer 21 for such a laser beam is large as described previously in connection with the formation of the conductive layers 5 and the non-single-crystal semiconductor layers 13. On the other hand, the conductive layer 21 is thin and its portion on the side of the non-single-crystal semiconductor layer 13 is constituted mainly of the sublimable metallic oxide, sublimable metallic non-oxide or sublimable metal, so that the conductive layers 23 are neatly formed, along with the grooves 22. That is to say, there is no possibilities that the underlying non-single-crystal semiconductor layers 13 are hollowed, by the laser beam, to form therein deep depression which in the prior art may sometime reach the underlying conductive layers 5, as indicated by 24 in Fig. 4B, and that the conductive layers 23 are exfoliated at their marginal edges, as indicated by 25 in Fig. 4C. Next, a passivation film 31 as of silicon nitride, which covers the conductive layers 23 and extends into the grooves 22, is formed by, for instance, a known plasma CVD method, and a protective film 32 of a synthetic resin is formed on the passivation film 31. In such a manner as described above, a semiconductor photoelectric conversion device 42 is fabricated in which a plurality of semiconductor photoelectric transducers 41, each comprising the conductive layer 5, the non-single-crystal semiconductor layer 13 and the conductive layer 23, are connected in series through the portions of the conductive layers 23 extending into the grooves 12. With the manufacturing method of the present invention described above, the conductive layer 5, the non-single-crystal semiconductor layer 13 and the conductive layer 23, which make up each semiconductor photoelectric transducer 41, can be easily formed with high accuracy and finely, without damaging them or exfoliating their marginal edges and without cracking the substrate 1. Further, the respective layers of each semiconductor photoelectric transducer 41 are isolated from the layers of the adjoining transducer 14 by a groove of a width substantially equal to the diameter of the laser beam, which is as small as 3 to 60 µm, so that a semiconductor photoelectric conversion device 42 can easily be manufactured in which a plurality of semiconductor photoelectric transducers 41 are arranged with a high density. While in the foregoing the present invention has been described as being applied to the manufacture of a semiconductor photoelectric conversion device, it will be apparent that the invention is applicable to the manufacture of various other semiconductor devices.

Claims: A method for the manufacture of a semiconductor device which includes a patterned transparent conductive film (3) of not more than one micron thickness formed on a glass substrate (1), said film comprising indium oxide, said method including the patterning of the conductive film by irradiation of the same with a laser beam so as selectively to remove predetermined portions (4) of the film and being characterized in that the laser which is utilized is a pulsed Excimer laser having a wavelength of 600nm or less and a pulse width of 50 nano-seconds or less and the mode of utilization of the laser is such as to effect removal of the film (3) by sublimation without substantially affecting the underlying glass surface (2). A method according to claim 1 wherein the laser beam has a spot diameter of 3 to 60µm. A method according to claim 1 or 2 wherein the transparent conductive film (3) comprises In₂0₃ or ITO (Indium-Tin Oxide) and the Excimer laser is an ArF laser having a wavelength of about 193nm, a KrF laser having a wavelength of about 248nm, a XeC1 laser having a wavelength of about 308nm, or a XeF laser having a wavelength of about 315nm. A method according to claim 1 or 2 or 3 wherein a non-single-crystal semiconductor layer (11) is formed on said transparent conductive film (3) and said semiconductor layer is patterned by irradiation of the same with a laser beam having a wavelength of 600nm or less so as selectively to remove predetermined portions (12) of the semiconductor layer. A method according to claim 4 wherein the non-single-crystal semiconductor layer (11) consists principally of a sublimable semiconductor such as Si, Si x Ge 1-x (where 0<x<0.5), Si x C 1-x (where 0<x<1), Si₃N 4-x (where 0<x<2) or Si0 2-x (where 0<x<1), includes hydrogen or a halogen as a dangling bond neutralizer and has a thickness of not more than one micron, and wherein the laser beam utilized for patterning the semiconductor layer is a YAG laser beam having a wavelength of about 530nm, an Excimer laser beam having a wavelength of about 193nm (ArF), about 248nm (KrF), about 308nm (XeCl) or about 315nm (XeF), an argon laser beam having a wavelength of about 514.5nm, about 488nm, about 458nm, about 363nm, or about 351nm, or a nitrogen laser beam having a wavelength of about 337nm. A method according to claim 4 wherein the laser beam utilized for patterning the semiconductor layer (11) is a pulsed Excimer laser beam having a wavelength of 600nm or less and a pulse width of 50 nano-seconds or less. A method according to claim 6 wherein the laser beam utilized for patterning the semiconductor layer has a spot diameter of 3 to 60µm. A method according to any of claims 4 to 7 wherein a non-transparent conductive layer (21) is formed on said semiconductor layer (11) and said non-transparent conductive layer is patterned by irradiation of the same with a laser beam having a wavelength of 600nm or less so as selectively to remove predetermined portions (22) of the non-transparent conductive layer. A method according to claim 8 wherein the non-transparent conductive layer (21) consists principally of a sublimable metal such as Cr or a Cr-Cu, Cr-Ag or Cr-N alloy and has a thickness of not more than one micron, and wherein the laser beam utilized for patterning the non-transparent conductive layer is a YAG laser beam having a wavelength of about 530nm, an Excimer laser beam having a wavelength of about 193nm (ArF), about 248nm (KrF), about 308nm (XeC1) or about 315nm (XeF), an argon laser beam having a wavelength of about 514.5nm, about 488nm, about 458nm, about 363nm or about 351nm, or a nitrogen laser beam having a wavelength of about 337nm. A method according to claim 8 wherein the laser bean utilized for patterning the non-transparent conductive layer (21) is a pulsed Excimer laser beam having a wavelength of 600nm or less and a pulse width of 50 nano-seconds or less. A method according to claim 10 wherein the laser bean utilized for patterning the non-transparent conductive layer has a spot diameter of 3 to 60µm. A method according to any of claims 8 to 11 wherein the transparent conductive film (3) is first formed on the substrate (1) and is patterned by irradiation with a laser to define at least two transparent conductive film portions (5) separated by a first groove (4), then the non-single-crystal semiconductor layer (11) is formed over the transparent conductive film so as to extend into said first groove (4) and is patterned by irradiation with a laser to define semiconductor layer portions (13) substantially overlying said transparent conductive film portions (5) and separated from each other by a second groove (12) and then the non-transparent conductive layer (21) is formed over the semiconductor layer so as to extend into the second groove and is patterned by irradiation with a laser to define non-transparent conductive film portions (23) substantially overlying said semiconductor layer portions (13) and separated from each other by a third groove (22), the method thereby producing a plurality of serially connected semiconductor elements each comprising a non-single-crystal semiconductor layer portion sandwiched between a transparent conductive film portion and a non-transparent conductive film portion.

Inventors: YAMAZAKI, SHUNPEI C/O SEMICONDUCTOR ENERGY
Applicants: SEMICONDUCTOR ENERGY LABORATORY CO., LTD.
Application year: 1984
Main classification: H01L21
IPC codes: H01L31, H01L21, C23C14, H01L27