Method of manufacturing a semiconductor device

Abstract: A semiconductor device has a device section (100) and a peripheral section (90) outside the device section. A main vernier pattern (30) is formed in the peripheral section for inspecting finely an alignment state in a first direction (e.g. X), and a subsidiary vernier pattern (130) is formed in the peripheral section near the main vernier pattern for inspecting coarsely an alignment state in a second direction (Y) at right angles to the first direction. Thus within a single field of view of a microscope, the misalignment can be detected in one direction with sufficient accuracy to provide a measurement correction, and in the other direction with enough accuracy to judge whether the product is good or bad.

Description: The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a process for inspecting whether a resist pattern is accurately aligned to a pattern formed beforehand. Semiconductor devices are manufactured by repeating a sequence of process steps which comprises forming a film, for example, a metal film entirely on a substrate in which a pattern, for example, a pattern of a field oxide layer has been already formed, forming a photoresist film entirely on the metal film, carrying out UV exposure in which ultra-violet rays are selectively irradiated on the photoresist film through a mask, developing the photoresist film to form a photoresist pattern, inspecting the alignment of the photoresist pattern to the pattern of the field oxide layer formed beforehand, and selectively etching the metal film to form a metal electrode wiring using the photoresist pattern as a mask when the photoresist pattern is confirmed by the inspecting process to be accurately positioned, that is, accurately aligned to the pattern of the field oxide layer. On the other hand, when the alignment of the photoresist pattern is determined to be wrong by the inspecting process, that is, the alignment is out of a permissible range, the photoresist pattern is completely removed without etching the metal film, and the device entirely re-worked from the step of forming a photoresist film. To inspect the alignment of the photoresist pattern with respect to the pattern formed beforehand, the pattern of the field oxide layer, a so-called vernier pattern technology is useful, in which a plurality of first rectangular patterns, in this case, oxide patterns, are formed with the forming of the field oxide layer pattern on a semiconductor substrate, in such a manner that the centers of the first patterns are spaced apart from each other at equal first distances in the widthwise direction thereof. A plurality of second rectangular patterns are formed of the photoresist film with the forming of the resist pattern for the metal wiring by the UV exposure through the mask, in such a manner that the centers of the second rectangular patterns are spaced apart from each other at equal second distances in the widthwise direction thereof. The second distance is different from the first distance by 0.1 µm, for example, and the center of the center rectangular pattern among the second rectangular patterns just coincides with the center of the center rectangular pattern among the first rectangular patterns when the resist pattern for forming the metal wiring is just aligned to the pattern of the field oxide layer. A worker visually examines through a microscope which pair of the first and second rectangular patterns coincide each other at their center. If the coinciding first and second patterns are the second ones from the center ones, the resist pattern for forming the metal wiring can be confirmed to be shifted by 0.2 µm from the desired position relating to the field oxide layer. The principle of the vernier pattern technology is essentially the same as that of vernier calipers. The vernier pattern including the first and second rectangular patterns is formed on a periphery portion of a device section in which semiconductor elements, wirings, bonding pads, etc. are formed, or is formed outside the device section such as on a chip dividing region or a scribe region such that these rectangular patterns are arranged in a first direction (horizontal direction in the plan view) to examine the alignment state in the first direction. Further, to examine the alignment state in a second direction (vertical direction in the plan view) another vernier pattern is provided on another portion outside the device section such that these rectangular patterns are arranged in the second direction. On the other hand, to evaluate the resist pattern all over the device section correctly, particularly, in a large chip or large device section such as has been the recent tendency, the vernier pattern for inspecting in the first direction is preferably provided near the center part of the outside section in the first direction along one edge of the device section, and the vernier pattern for inspecting in the second direction is preferably provided near the center area of the outside section in the second direction along another edge of the device section. As a result, the vernier pattern for the first direction and the vernier pattern for the second direction are separated from each other at a large distance. Therefore, we have appreciated that when the alignment inspection in the first direction is conducted by a microscope, any vernier pattern for the second direction cannot be seen in the visual field of the microscope. In consequence, the time required for the step of checking the amount of resulting misalignment is increased in the manufacturing process, thus causing lowering in the processing capacity of the production line. This may be seen from Fig. 1 of the drawings, in which a plurality of device sections 100 to 400 are formed on a silicon substrate (semiconductor wafer) 1, and each of the device sections is surrounded by peripheral sections of the substrate, constituting a chip dividing region (scribe region) 90 of grid-like shape with first to fourth boundary lines 11 to 14. The first and third lines 11 and 13 extend in an X-direction and the second and fourth lines 12 and 14 extend in a Y-direction at right angles to the X-direction. A plurality of active and passive elements, electrode wirings, bonding pads, etc. are formed in the device section. However, only one transistor 20 is exemplified. The transistor 20 includes source, drain and channel regions formed in an active region 22 surrounded by a thick field silicon oxide layer 21, a gate electrode 23 of polycrystalline silicon (hereinafter called a polysilicon) formed on the channel region via a gate insulating film, and metallic wirings 24 connected to the source and drain regions and to the gate electrode, respectively. On the other hand, on the chip dividing section 90, vernier patterns 30 are formed along the boundary lines 11 to 14 near their centers 11' to 14'. Referring to Fig. 2, each of the vernier patterns 30 comprises a first check pattern 40 including nine rectangular patterns arranged in the X-direction (or Y-direction) and their centers are spaced apart from each other at equal distance of 10.0 µm, a second check pattern 60 including nine rectangular patterns arranged in the X direction (or Y-direction) and their centers are spaced apart from each other at equal distance of 9.9 µm, and an indicium pattern 80 indicating the center pair of the rectangular patterns. The first check pattern 40 and the indicium pattern 80 are formed with the formation of the field oxide layer 21 in the device section, and the second check pattern 60 is formed with the formation of the gate electrode 23. Therefore, for example, if the centers of the rectangular patterns of the first and second check patterns coincide at the center pair as shown in Fig. 2, the gate electrode 23 is confirmed to be aligned to the field insulating layer pattern 21, that is, to the active region 22. On the contrary, if their centers coincide at the third pair from the center pair, one can recognize that the gate electrode 23 is shifted from the precise position by 0.3 µm in the X-direction (or Y-direction). The use of verniers is described for example in IBM Technical Disclosure Bulletin, Vol. 26, No. 9, February 1984, pages 4855-4859, "Method and Apparatus of In Situ Measurement and Overlay Error Analysis for Correcting Step and Repeat Lithographic Cameras", H. Herd and L. Jacobwitz. The use of verniers is further described in US-A-4 529 314. In detail, US-A-4 529 314 discloses a method of manufacturing a semiconductor device having a semiconductor substrate, the substrate including a plurality of device sections. The method comprises the step of forming a first device pattern on at least one of the device sections and a first check pattern, the first check pattern comprising a first main pattern which consists of a first number of rectangular patterns such that their centres are equally spaced apart from each other by a first distance in the widthwise direction and arranged in the first direction, and a first subsidiary pattern provided in the vicinity of the first main pattern and which consists of a second number of rectangular patterns such that their centres are equally spaced apart from each other by a second distance in the widthwise direction and arranged in a second direction at right angles to the first direction. The method further comprises the step of forming a second device pattern on a resist layer on a film and on the device section and a second check pattern on the resist layer on the film by selective irradiation of rays on the resist layer followed by development of the resist layer, and inspecting the relative positions of the first and second main patterns and of the first and second subsidiary patterns with a microscope. The second check pattern comprises a second main pattern which consists of the first number of rectangular patterns such that their centres are equally spaced apart from each other by a third distance different from the first distance in the widthwise direction and arranged in the first direction, each rectangular pattern of the second main pattern being formed on or positioned near a corresponding rectangular pattern of the first main pattern to form the first number of pairs thereby forming a main vernier pattern, and a second subsidiary pattern which consists of the second number of rectangular patterns such that their centres are equally spaced apart from each other by a fourth distance different from the second distance in the widthwise direction and arranged in the second direction, each rectangular pattern of the second subsidiary pattern being formed on or positioned near a corresponding rectangular pattern of the first subsidiary pattern to form the second number of pairs thereby forming a subsidiary vernier pattern. The subsidiary vernier pattern is provided in the vicinity of the main vernier pattern such that the main and subsidiary patterns can be seen within a field of view of the microscope used during the step of inspecting. The second number of rectangular patterns is equal to the first number of rectangular patterns. The present invention is defined in claim 1 below, to which reference should now be made. Advantageous features of the invention are set forth in the appendant claims. A preferred embodiment of the invention is described in more detail below with reference to the drawings, and takes the form of a semiconductor device with a device section and a peripheral section outside the device section. A main vernier pattern is formed in the peripheral section for finely inspecting the alignment state in a first direction (e.g. X), and a subsidiary vernier pattern is formed in the peripheral section near the main vernier pattern for coarsely inspecting the alignment state in a second direction (Y) at right angles to the first direction. Thus, within a single field of view of a microscope, the misalignment can be detected in one direction with sufficient accuracy to provide a measurement correction, and in the other direction with enough accuracy to judge whether the product is good or bad. Each vernier pattern is formed of rectangular patterns. If the number of patterns forming the main vernier pattern is nine, and the number forming the subsidiary vernier pattern is five, the main vernier pattern has spacings of 10.0 µm and 9.9 µm for its two halves and the subsidiary vernier pattern has spacings of 10.0 µm and 9.8 µm for its two halves, then the main vernier pattern has the capability of detecting a misalignment in the first direction with an accuracy of 0.1 µm, from -0.4 µm to +0.4 µm, and the subsidiary vernier pattern is capable of detecting a misalignment in the second direction with an accuracy of 0.2 µm, from -0.4 µm to +0.4 µm. Thus, a subsidiary vernier pattern is provided in the vicinity of the main vernier pattern, the subsidiary vernier pattern being coarser and lower in terms of resolution capability than the main vernier pattern, and this combination of main and subsidiary verniers is preferably provided for each of the two detection purposes, that is, the detection of a misalignment in a first direction and the detection of a misalignment in a second direction. Therefore, in this embodiment misalignments in the two orthogonal directions can be detected within one field of view of a microscope, in such a manner that, for one direction, the misalignment detection can be effected with a degree of accuracy such that the detected amount of misalignment can be fed back to an alignment device of a step-and-repeat apparatus, and, for the other direction, the detection can be effected with such a degree of accuracy that it is possible to judge whether the product is good or bad. Further, since the main vernier pattern is different in size from the subsidiary vernier pattern, there is no fear that the two verniers will be mistaken from each other. In addition, since the subsidiary vernier pattern may be coarse, the size thereof can be reduced, and therefore, the space required to install it can be minimized. For example, the subsidiary vernier pattern can be formed with the main vernier pattern in one chip dividing region, or one scribe region, which extends along one edge line of the device section. The material forming the first half of the vernier patterns may be an insulating material such as silicon oxide or silicon nitride, and the material forming the second half of the vernier patterns may be a conductive material such as polycrystalline silicon, aluminum, refractory metal (high melting point metal) (W, Mo, Ta, Ti) or alloy thereof. The invention will now be described in more detail, by way of example, with reference to the drawings, in which: Fig. 1 (described above) is a plan view showing a semiconductor device manufactured by a known method; Fig. 2 (described above) is an enlarged plan view showing a portion of Fig. 1; Fig. 3 is a plan view showing a semiconductor device manufactured by a method of an embodiment of the present invention; Fig. 4 is an enlarged plan view showing a portion of Fig. 3; and Figs. 5 to 9 are drawings showing process steps of the embodiment of the present invention, in which Figs. 5A, 6A, 8A and 9A are plan views showing a device section of a substrate, and Figs. 5A', 6A', 8A' and 9A' are cross-sectional views taken along lines E-E' in Figs. 5A, 6A, 8A and 9A as viewed in the direction of the arrows, respectively; Figs. 5B, 6B, 8B and 9B are plan views showing a peripheral section of the substrate, and Figs. 5B', 6B', 8B' and 9B' are cross-sectional views taken along lines F-F' in Figs. 5B, 6B, 8B and 9B as viewed in the direction of the arrows, respectively; and Fig. 7 is a cross-sectional view of the peripheral section of the substrate and a drawing schematically showing a reduction projection exposure in a step-and-repeat apparatus. Referring to Figs. 3 and 4, the same components as those in Figs. 1 and 2 are indicated by the same reference numerals. In addition to the main vernier pattern 30, a subsidiary vernier pattern 130 is formed near the main vernier pattern 30. The subsidiary vernier pattern 130 comprises a first subsidiary pattern 140 including five rectangular patterns arranged in the Y-direction (or X-direction) and their centers in the width-wise direction are spaced apart from each other at equal distance of 10.0 µm, a second subsidiary pattern 160 including five rectangular patterns arranged in the Y-direction (or X-direction) and their centers in the width-wise direction are spaced apart from each at equal distance of 9.8 µm, and an indicium pattern 180 indicating the center pair of the rectangular patterns. The first subsidiary pattern 140 and the indicium pattern 180 of the subsidiary vernier pattern 130 are formed with the formation of the field oxide layer 21 in the device section and with the first main pattern 40 and the indicium pattern 80 of the main vernier pattern 30, and the second subsidiary pattern 160 of the subsidiary vernier pattern 130 is formed with the formation of the gate electrode 23 and with the second main pattern 60 of the main vernier pattern 30. Therefore, in addition to the fine checking of the alignment in the X-direction (or Y-direction) by the main vernier pattern 30, a coarser checking of the alignment in the Y-direction (or X-direction) by the subsidiary vernier pattern 130 can be conducted when the fine checking by the main vernier pattern 30 is conducted, within the same visual scope of a microscope. That is, for example, if the centers of the rectangular patterns of the first and second subsidiary patterns 140, 160 coincide at the center pair as shown in Fig. 4, the gate electrode 23 is aligned to the field insulating layer pattern 21, that is, to the active region 22 in the Y-direction (or X-direction). To the contrary, if their centers coincide at the second pair (end pair) from the center pair, one can recognize that the gate electrode 23 is shifted from the precise position by 0.4 µm in the Y-direction (or X-direction). It is to be noted that the explanations are under an assumption that when the patterns in the device section are accurately aligned from each other in the X- and Y-directions, the centers of the rectangular patterns coincide at the center pair indicated by the indicium pattern 80 in the main vernier 30 and the centers of the rectangular patterns coincide at the center pair indicated by the indicium pattern 180 in the subsidiary vernier 130, respectively. Next, a method of the embodiment will be explained by referring Figs. 5 to 9. At first, through a photo-lithography step using a mask and an oxidation step, the first main pattern 40, the main indicium pattern 80, the first subsidiary pattern 140 and subsidiary indicium pattern 180 are formed on the peripheral section 90 of the silicon substrate 1 by a thick silicon oxide layer protruding from the major surface of substrate with the formation of the thick field silicon oxide layer 21 on the device section 100 surrounding the active region 22, and thereafter thin silicon oxide films 25, used as the gate insulating film under the gate electrode, are formed where the thick silicon oxide layers are absent. The first main pattern 40 is composed of first to ninth rectangular patterns 41 to 49 each having a width W of 2.0 µm and a length L of 15 µm. The patterns 41 to 49 are arranged in the X-direction and their centers 41' to 49' in the widthwise are spaced apart from each other at a distance A of 10.0 µm. The first subsidiary check pattern 140 is composed of first to fifth rectangular patterns 141 to 145 each having a width W of 2.0 µm and a length L of 15 µm. The patterns 141 to 145 are arranged in the Y-direction and their centers 141' to 145' in the widthwise direction are spaced apart from each other at a distance B of 10.0 µm (Fig. 5). Next, a polysilicon film 27 is entirely formed, and a positive photo-resist layer 28 is entirely formed on the polysilicon film (Fig. 6). Next, as shown in Fig. 7, the resist layer 28 is selectively irradiated by ultra-violet (UV) rays through a reticle mask by a reduction projection exposure apparatus of a step-and-repeat system on the device section 100 and on the peripheral sections 90 to form necessary resist patterns on the device and peripheral sections after development. Returning to Fig. 3, in the step-and-repeat exposure, the resist layer on the peripheral section along the first and second boundary lines 11, 12 are irradiated with the resist layer on the device section 100 by one shot of the irradiation, and the resist layer on the peripheral section along the third and fourth boundary lines 13 and 14 are irradiated with device sections 300 and 200 by other shots of the irradiation after moving relatively the wafer, respectively. Next, by developing the positive photoresist layer which was selectively irradiated, a photo-resist pattern 29 by the resist layer 28 for forming the polysilicon gate electrode 23 is formed on the device section 100, and a second main pattern 50 by the resist layer 28 and a second subsidiary pattern 150 by the resist layer 28 are formed on the peripheral section 90. The second main pattern 50 is composed of first to ninth rectangular or stripe patterns 51 to 59 each having a width W' of 1.5 µm and a length L' of 15 µm. The pattern 51 to 59 are arranged in the X-direction and their centers 51' to 59' in the widthwise are spaced apart from each other at a distance C of 9.9 µm. Further, every rectangular pattern of the photo-resist layer belonging to the second main pattern 50 is formed partially on corresponding rectangular pattern of the protruding silicon oxide layer belonging to the first main pattern 40 to constitute nine pairs of patterns of first and second main patterns. The subsidiary pattern 150 is composed of first to fifth rectangular or stripe patterns 151 to 155 each having a width W' of 1.5 µm and a length L' of 15 µm. The patterns 151 to 155 are arranged, in the Y-direction and their centers 151' to 159' in the widthwise direction are spaced apart from each other at a distance D of 9.8 µm. Further, every rectangular pattern of the photo-resist layer belonging to the second subsidiary pattern 150 is formed partially on the corresponding rectangular pattern of the protruded silicon oxide layer belonging to the first subsidiary pattern 140 to constitute five pairs of patterns of first and second subsidiary patterns. Thereafter, a worker inspects the main vernier pattern constituted by the first and second main patterns 40, 50 by a microscope with respect to what pair of the rectangular patterns coincide their centers. For example, if the resist pattern 55 and the oxide pattern 45 are observed to coincide at their centers 55', 45' as shown in Fig. 8B, the resist pattern 24 for forming the gate electrode is precisely aligned, in the X-direction, to the insulating layer pattern 21, that is, to the active region pattern 22. On the contrary, if the resist pattern 58 and oxide pattern 48 would be observed to coincide at their centers 58', 48', the resist pattern 24 is determined to be shifted from the precise position by 0.3 µm in the X-direction. Thus, the subsidiary vernier pattern constituted by the first and second subsidiary patterns 140, 150 can be also inspected when the main vernier pattern is inspected within the same visual scope or field of the microscope. For example, if the resist pattern 153 and the oxide pattern 143 are observed to be coincided at their centers 153', 143' as shown in Fig. 8B, the resist pattern 24 for forming the gate electrode is aligned, in the Y-direction, to the insulating layer pattern 21, that is, to the active region pattern 22. To the contrary, if the resist pattern 155 and oxide pattern 145 would be observed to coincide at their centers 155', 145', the resist pattern 24 is determined to be shifted from the precise position by 0.4 µm in the Y-direction. When the alignment of the resist pattern is within a permissible range in both of X and Y-directions, an etching process is carried out to remove selectively the polysilicon film 27 using the resist patterns as a mask so as to form the gate electrode 23 on the device section, and to form the main and subsidiary conductive patterns 60 and 160 composed of rectangular patterns 61 to 69 and 161 to 165, having the same shape and position as the resist patterns 51 to 59 and 151 to 155, respectively, on the peripheral section 90 (Fig. 9 and Figs. 3, 4). On the other hand, when the alignment is out of the permissible range, the resist pattern is completely removed without etching the polysilicon film 27 to entirely re-work the device from the step of forming a resist film.

Claims: A method of manufacturing a semiconductor device having a semiconductor substrate, the substrate including a plurality of device sections formed adjacent to each other, a device section having a first boundary line extending in a first direction, and a first peripheral section outside and adjacent the said first boundary line, and laying between adjacent device sections, the method comprising the steps of: forming a first device pattern on at least one of the device sections and a first check pattern on said first peripheral section, the first check pattern comprising a first main pattern which consists of a first number of rectangular patterns such that their centers are equally spaced apart from each other by a first distance in the widthwise direction and arranged in the first direction, and a first subsidiary pattern which consists of a second number of rectangular patterns, less than the first number, such that their centers are equally spaced apart from each other by a second distance in the widthwise direction and arranged in a second direction at right angles to the first direction; forming a film entirely on the substrate; forming a resist layer entirely on the film and on the substrate; forming a second device pattern on the resist layer on the film and on said device section and a second check pattern on the resist layer on the film and on the first peripheral section by selective irradiation of rays on the resist layer followed by development of the resist layer, the second check pattern comprising a second main pattern which consists of the first number of rectangular patterns such that their centers are equally spaced apart from each other by a third distance different from the first distance in the widthwise direction and arranged in the first direction, each rectangular pattern of the second main pattern being formed on or positioned near a corresponding rectangular pattern of the first main pattern to form the first number of pairs thereby forming a main vernier pattern, and a second subsidiary pattern which consists of the second number of rectangular patterns such that their centers are equally spaced apart from each other by a fourth distance different from the second distance in the widthwise direction and arranged in the second direction, each rectangular pattern of the second subsidiary pattern being formed on or positioned near a corresponding rectangular pattern of the first subsidiary pattern to form the second number of pairs thereby forming a subsidiary vernier pattern different in size to the main vernier pattern, said subsidiary vernier pattern being coarser and lower in terms of resolution capability than the main pattern; and inspecting the relative positions of the first and second main patterns and of the first and second subsidiary patterns with a microscope, wherein the subsidiary vernier pattern is provided in the vicinity of the main vernier pattern such that the main and subsidiary patterns can be seen within a field of view of the microscope during the step of inspecting. A method of manufacturing a semiconductor device according to claim 1, in which the device section has a second boundary line which extends in the second direction, and a second peripheral section is provided outside and adjacent the second boundary line and between adjacent device sections; a third check pattern is formed on the second peripheral section in the said step of forming the first device pattern on the device section, the check pattern on the second peripheral section having a similar shape to the first check pattern on the first peripheral section but its main pattern being arranged in the second direction and its subsidiary pattern being arranged in the first direction; and a fourth check pattern of the resist layer is formed on the second peripheral section in the said step of forming a second device pattern of the resist layer on the device section, the fourth check pattern on the second peripheral section having a similar shape to the second check pattern on the first peripheral section but its main pattern being arranged in the second direction and its subsidiary pattern being arranged in the first direction. A method of manufacturing a semiconductor device according to claim 1 or 2, in which the fourth distance is less than the third distance, and the first and second distances are equal to each other. A method of manufacturing a semiconductor device according to claim 1, 2 or 3, in which the third distance is less than the first distance, and the fourth distance is less than the second distance. A method of manufacturing a semiconductor device according to any preceding claim, further comprising the step of selectively removing the film using the second device pattern of the resist layer and the second check pattern of the resist layer as a mask, when the second device pattern is determined by the inspecting step to be aligned to the first device pattern within a permissible range. A method of manufacturing a semiconductor device according to any preceding claim, further comprising the step of removing the second device pattern of the resist layer and the second check pattern of the resist layer without removing the film to re-work the device from the step of forming a resist layer, when the alignment of the second device pattern to the first device pattern is determined by the inspecting step to be out of a permissible range. A method of manufacturing a semiconductor device according to any preceding claim, in which the first device pattern is a field oxide layer pattern protruding from a major surface of the substrate, and the first check pattern is made of oxide layer protruding from the major surface as the field oxide layer. A method of manufacturing a semiconductor device according to claim 7, in which the film is an electrically conductive film to form an electrode wiring on the device section. A method of manufacturing a semiconductor device according to any preceding claim, in which the peripheral section is a chip dividing region.

Inventors: NISHIMOTO SHOZO, NISHIMOTO, SHOZO
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1989
Main classification: G03F9
IPC codes: G01D13, G03F7, H01L21, G03F9