Source: https://patents.google.com/patent/DE102008007671B4/en
Timestamp: 2019-11-22 16:29:50
Document Index: 44123358

Matched Legal Cases: ['arts 124', 'arts 124', 'arts 124', 'arts 124', 'arts 124', 'arts 124']

DE102008007671B4 - Process for forming fine structures of a semiconductor device - Google Patents
Process for forming fine structures of a semiconductor device
DE102008007671B4
DE102008007671B4 DE102008007671.6A DE102008007671A DE102008007671B4 DE 102008007671 B4 DE102008007671 B4 DE 102008007671B4 DE 102008007671 A DE102008007671 A DE 102008007671A DE 102008007671 B4 DE102008007671 B4 DE 102008007671B4
DE102008007671.6A
DE102008007671A1 (en
2007-02-06 Priority to KR10-2007-0012347 priority Critical
2007-02-06 Priority to KR1020070012347A priority patent/KR100843236B1/en
2008-09-11 Publication of DE102008007671A1 publication Critical patent/DE102008007671A1/en
2018-07-26 Publication of DE102008007671B4 publication Critical patent/DE102008007671B4/en
2028-01-26 Anticipated expiration legal-status Critical
A method of forming fine structures of a semiconductor device, comprising the steps of: forming a hard mask layer (124) in a first region (A) and a second region (B) of a substrate (100) including an etching film (120) to be etched Forming a plurality of mask patterns (130, 150a) and a buffer layer (140) on the hard mask layer (124), wherein the plurality of mask patterns (130, 150a) are repeatedly formed by forming a first pattern density in the first area (A ) and having a second pattern density greater than the first pattern density in the second region (B), and wherein the buffer layer (140) covers both sidewalls of the mask patterns (130, 150a) in the second region (B), first etching by reactive ion etching (RIE) of the buffer layer (140) and the hard mask layer (124) in both the first region (A) and the second region (B) under a first etch environment until a first Surface of the etching film (120) in the first region (A) is exposed using the mask patterns (130, 150a) as an etching mask, second etching for forming hard mask patterns (124b) under a state where the first surface of the etching film (120 ) is exposed in the first region (A) and the etching film (120) is not exposed in the second region (B) by etching the hard mask layer (124) until the second surface of the etching film (120) in the second region (B ), wherein a second etch environment is used to produce polymer byproducts (160) that accumulate on the first surface of the etch film (120) exposed in the first region (A), the mask structures in the first etching environment, removing the polymer by-products (160) accumulated on the first surface to expose the first surface of the etching film (120), and forming etching film patterns (120a) by etching the exposed one the first surface and the second surface of the etching film (120) using the hard mask patterns (124b) as an etching mask.
The invention relates to a method for forming fine structures of a semiconductor device.
Manufacturing highly integrated semiconductor devices requires highly miniaturized structures. To integrate many elements into a small area, the individual elements must be small in size. The small dimensions can be achieved by reducing the pitch of a structure, which is the sum of the width and pitch between adjacent structures to be formed later. At present, the drastic reduction in the design rules of semiconductor devices has reached a limit on the formation of fine-pitch structures due to resolution limitations of photolithography. Specifically, forming desired fine-pitch structures due to the resolution limitations of photolithography has reached a limit when forming a device isolation region defining an active region in a substrate or forming a line and space pattern (hereinafter referred to as "L / S Structure ") photolithography is used.
In order to overcome the above-mentioned resolution limitations of photolithography, methods for forming hard mask patterns having a fine pitch and using a double pattern have been proposed. However, when it is intended to form a given structure simultaneously in an area having a relatively high pattern density such as a cell array area and a region having a relatively small pattern density such as a peripheral circuit area or a core area, it is necessary to develop a double patterning. wherein a desired pattern having different pitches is formed for each area, so that the double patterning can be selectively applied only to the area having the higher pattern density.
In particular, when the structures having different pitches are simultaneously formed in respective areas having pattern densities different from each other, each area must have a different etch rate per area due to a difference in pattern densities. Due to the different etching rates per area caused by the difference in the pattern densities, a film thickness removed by subsequent etching may be different depending on the pattern densities of respective areas. As a result, no desired pattern shapes can be obtained due to the difference of the pattern densities in respective regions. Therefore, new double-structuring techniques are required that can solve the problems that may occur when removing a film that has different thicknesses due to pattern densities, particularly when it is intended to form predetermined patterns simultaneously in a plurality of areas.
The publication US 2006/0 234 166 A1 discloses a method of forming fine structures of a semiconductor device comprising forming a first hard mask pattern having a plurality of first line patterns on an etching film to be etched in first and second areas of the substrate, forming a first layer on sidewalls, and a top of the first hard mask pattern a depression at the top between two adjacent first line patterns, the formation of a second hardmask structure having a plurality of second line patterns within the recess, performing an anisotropic etch process of the first layer using the first and second line patterns as an etch mask to expose the etch film to be etched the first and second line patterns and performing another anisotropic etching process for etching the etching film using the first and second hard mask patterns as the etching mask.
The invention is based on the technical problem of providing a method for forming fine structures of a semiconductor device capable of reducing or avoiding the above-mentioned difficulties of the prior art, and which in particular allows structures with a fine pitch over typical Resolution limitations of photolithography addition.
The invention solves this problem by providing a method having the features of claim 1. Advantageous developments of the invention are specified in the subclaims.
The method according to the invention prevents problems arising due to a difference in thickness of a film to be removed from each region of a plurality of regions having different pattern densities when structures having various dimensions at different pitches using double patterning to perform structures with a fine Pitch, which can overcome resolution limitations of photolithography, are formed simultaneously on an identical substrate.
Even if a film that is to be etched in areas with different structural densities, has different thicknesses, a transfer caused by the thickness difference stages according to the invention can be effectively prevented. As a result, structures having a fine pitch that overcome resolution limitations of photolithography can be easily obtained.
Advantageous embodiments of the invention are described below and shown in the drawings, in which:
1A to 1K Are cross-sectional views illustrating a method of forming fine structures of a semiconductor device, and
2 FIG. 12 is a graph illustrating a result of measuring an etching quantity of an oxide film according to a flow rate of O 2 of an etchant used for double etching when patterning a hard mask layer in a method of forming fine structures of a semiconductor device.
It should be understood that when an element or layer is referred to as being "on," "connected to," or "coupled to" another element or layer, it will be directly attached to, coupled to or coupled to the other element or layer may be the other layer or intervening elements or layers may be present. In contrast, there are no intervening elements or layers when an element is referred to as being "directly on," "directly connected to," or "directly coupled to" another element or layer. Deviations from shapes shown in the illustrations, for example, as a result of manufacturing techniques and / or tolerances may be expected in actual embodiments. For example, an implanted region shown as a rectangle typically has rounded or curved features and / or a gradient of implant concentration at its edges, rather than a binary change from the implanted to the unimplanted region, at its edges. Similarly, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which implantation takes place.
The 1A to 1K illustrate a method of forming fine structures of a semiconductor device according to an embodiment of the invention. Referring to FIG 1A becomes an etching film 120 to be etched in both a low density structural area A and a high density structural area B of a substrate 100 educated. The substrate 100 may be a conventional semiconductor substrate.
The structural area A of the substrate 100 low-density has a relatively small pattern density per unit area, and may be in a peripheral circuit area or a core area, for example. Otherwise, the low density structure region A may be part of the cell field regions where desired structures have a relatively low density per unit area. The high-density structural area B has a structural density per unit area higher than that of the low-density structural area A, and may be part of the cell array areas, for example.
The etching film 120 may be a conductive layer or an insulating layer for forming a plurality of patterns repeatedly formed with a fine pitch to form the semiconductor device and may be made of a metal, a semiconductor or an insulating material. The etching film 120 For example, it may be tungsten (W), tungsten silicide, polysilicon, aluminum (Al), or a combination of these materials. When insulating regions formed repeatedly with a fine pitch are included in the semiconductor substrate 100 can be formed, the etching film 120 be omitted. In the present embodiment, the formation of fine structures from the etching film becomes 120 as an example.
On the etching film 120 becomes a hardmask layer 124 educated. The hard mask layer 124 can be different from different materials. For example, the hard mask layer 124 an oxide film, a nitride film, or a combination of these films. Otherwise, there is the hard mask layer 124 when the etching film 120 is an insulating film or a conductive film made of a material corresponding to the material of the etching film 120 may have an etch selectivity. For example, the hard mask layer 124 an oxide film selected from the group consisting of a thermal oxide film, a chemical vapor deposition (CVD) oxide film, an undoped silicate glass (USG) film, and a high-density plasma (HDP) oxide film. Otherwise, the hard mask layer 124 be a single film selected from the group consisting of SiON, SiN, SiBN and BN. Furthermore, the hard mask layer 124 be a multi-layer formed of at least one oxide film selected from the above-mentioned oxide films and at least one nitride film selected from the above-mentioned nitride films.
Referring to 1B becomes a plurality of first mask patterns using conventional photolithography 130 on the hard mask layer 124 educated. The first mask structures 130 are repeatedly formed with a first pitch P A which is equal to a pitch P A of structures finally on the etching film 120 in the structural area A of the substrate 100 should be formed with low density. In the structural region B of the substrate 100 high density become the first mask structures 130 repeatedly formed with a second pitch 2P B which is twice a pitch P B of structures to be finally formed on the etch film 120.
A first width W 1 of the first mask structures 130 may be ¼ of the second pitch 2P B in the structural area B with high density. The first mask structures 130 may be a plurality of line structures having the second pitch 2P B , for example repeated in a predetermined direction on the substrate 100 be formed.
When the hard mask layer 124 is an oxide film, the first mask structures 130 a polysilicon film or a nitride film including, but not limited to, SiON, SiN, SiBN and BN. Alternatively, the first mask structures 130 For example, consist of an oxide film when the hard mask layer 124 is a nitride film.
Referring to 1C becomes the hardmask layer 124 that exist between the first mask structures 130 is exposed in the low density structural area A and the high density structural area B from an upper surface of the hard mask layer 124 removed from a first thickness d to underside parts 124a to build. Furthermore, the first thickness d may be equal to the first width W 1 of the first mask structures 130 be formed in the structure area B with high density.
At the top of the hardmask layer 124 a dry etching process can be performed to the bottom parts 124a to build. If, for example, referring to 1B described first mask structures 130 are formed after the formation of the first mask structures 130 performed an over-etching, so that the underside parts 124a can be formed by dry etching. Alternatively, a dry etching process for forming the lower side parts 124a may be performed separately.
Referring to 1D becomes a buffer layer 140 on the first mask structures 130 and the hardmask layer exposed between the first mask patterns 130 124 educated. The buffer layer 140 covers the tops and sidewalls of the first mask structures 130 and the bottom parts 124a the hard mask layer 124 with a uniform thickness. In addition, the buffer layer 140 the first mask structures 130 and the bottom parts 124a the hard mask layer 124 with a thickness equal to the first thickness d. Furthermore, the thickness of the buffer layer 140 be set to have a second width W 2 of recesses 142 equal to the first width W 1 of the first mask structures 130 makes, which are formed in the structural area B with high density.
In the high density structural area B, the buffer layer covers 140 the tops and sidewalls of the first mask structures 130 with a uniform thickness. In addition, the widths a and b of the buffer layer 140 showing the first mask structures 130 covered, in the high density structural area B, equal to 1/4 of the second pitch 2P B , that is, the first width W 1 of the first mask patterns 130 , As a result, the pits become 142 in the high density structural region B in the upper part of the buffer layer 140 between two adjacent first mask structures 130 under the first mask structures 130 formed as shown.
When a distance between two adjacent first mask structures 130 under the first mask structures 130 in the structural area A of low density is smaller than that in the structural area B of high density, that is, when a distance d 1 between two adjacent first mask structures 130 smaller than a sum of the widths a and b of the buffer layer 140 is the two sidewalls of the first mask structures 130 in the structural area B covered with high density, that is, [d 1 <a + b] becomes the pit 142 within the range of the distance d 1 not in the top of the buffer layer 140 formed as in 1D shown.
In addition, if the distance between two adjacent first mask structures 130 under the first mask structures 130 in the structural area A of low density is larger than that in the structural area B of high density, especially if a distance d 2 between two adjacent first mask structures 130 greater than twice the sum of the widths a and b of the buffer layer 140 which is the side walls of the first mask structures 130 in the structural region B at high density, that is, [d 2 > 2 (a + b)], the recesses 142 become in the top of the buffer layer 140 is formed within a range of the distance d 2 , as in 1D shown.
The buffer layer 140 acts as a buffer around the heights of the first mask structures 130 , later used as an etching mask to structure the Hard mask layer 124 are used, equal to the heights of the second mask structures 150a (please refer 1F ) in a subsequent process later within the wells 142 be formed.
The buffer layer 140 may be made of a material having etching characteristics similar to that of the hardmask layer 124 are. The buffer layer 140 may for example consist of a material that the hard mask layer 124 forms. Otherwise, the buffer layer 140 are made of another material having etching characteristics similar to those of the hardmask layer 124 are. As an example, each of the hard mask layers 124 and the buffer layer 140 consist of oxide. In addition, the buffer layer 140 an oxide film or a nitride film formed by an atomic layer deposition (ALD) method. When the first mask structures 130 are a polysilicon film, the hard mask layer 124 alternatively a plasma enhanced oxide (PEOX) film, and the buffer layer 140 may be an oxide film formed by the ALD method.
Referring to 1E becomes a second mask layer 150 on the buffer layer 140 educated. The second mask layer 150 may be made of a material having etching characteristics similar to those of the first mask patterns 130 are. The second mask layer 150 can be made of a material that is identical to that of the first mask structures 130 forms or another material with similar Ätzcharakteristika. For example, each of the first mask patterns 130 and the second mask layer 150 a polysilicon film. In addition, the first mask structures 130 be a nitride film, and the second mask layer 150 may be a polysilicon film and vice versa.
The wells 142 in the high density structural area B, that in the top of the buffer layer 140 are formed with the second mask layer 150 filled. When the widths a and b of the buffer layer 140 showing the sidewalls of the first mask structures 130 covered, 1/4 of the second pitch 2P B , the second width W 2 of the second mask layer 150 in the wells 142 in the structural area B is filled with high density, 1/4 of the second pitch 2P B , ie equal to the first width W 1 of the first mask structures 130 be. The second mask layer 150 extends within the recesses 142 in the same direction, in which the first mask structures 130 extend.
When the distance between two adjacent first mask structures 130 is small in the structural area A with low density, ie when the distance d 1 between the first mask structures 130 smaller than the sum of the widths a and b of the buffer layer 140 is, that is, [d 1 <a + b], the second mask layer extends 150 within the distance d 1 not into the recesses 142 because in the top of the buffer layer 140 no recess is formed when the widths a and b of the buffer layer 140 showing the sidewalls of the first mask structures 130 covered, 1/4 of the first pitch 2P B , as described above. However, if a distance between the two adjacent first mask structures 130 in the structure region A of low density is larger than that of the structure region B of high density, and especially the distance d 2 between the two adjacent first mask structures 130 greater than twice the sum of the widths a and b of the buffer layer 140 which is the side walls of the first mask structures 130 covered, that is, [d 2 > 2 (a + b)] is the top of the second mask layer 150 within a range included in the distance d 2 after the second mask layer 150 in the specialization areas 142 is formed in the top of the buffer layer 140 are formed, and the recesses 142 are through the steps on the second mask layer 150 partly uncovered by a predetermined width W 3 , as in 1E shown.
Referring to 1F becomes the second mask layer 150 partially removed to within the pits 142 in the high density structural area B, the second mask patterns 150a to build. Thus, within the pits 142 formed in the structure area B with high density, a plurality of line structures, which are the second mask structures 150a which are identical to the first mask structures 130 extend. In addition, the buffer layer becomes 140 exposed the first mask structures 130 between the second mask structures 150a covered. The second mask patterns 150a formed in the recesses 142 remain in the high-density structure area B are at approximately the same horizontal plane of the first mask patterns 130 arranged as in 1F shown.
In addition, the second mask layer becomes 150 that are within the pits 142 is located in the low-density structural region A continuously from a region where the distance d 2 between the two adjacent first mask structures 130 is defined as d 2 > 2 (a + b), as well as the part of the second mask layer 150 on top of the buffer layer 140 removed, as in 1F shown. As a result, the buffer layer becomes 140 showing the first mask structures 130 covered completely exposed in the structure area A with low density.
If the second mask layer 150 is partially removed, an etch quantity of the first mask structures 130 be adjusted so that the tops of the second mask structures 150a at the same level as the tops of the first mask structures 130 in the structural area B with high density. For example, to partially remove the second mask layer 150, wet etching may be performed.
Referring to 1G becomes the buffer layer 140 which is exposed, ie the part of the buffer layer 140 which is the tops of the first mask structures 130 covered, removed, around the tops of the first mask structures 130 in both the low density structural area A and the high density structural area B. Then, the high density structural region B has a structure in which the tops of the first mask patterns 130 and the tops of the second mask structures 150a are uncovered together.
In this case, the etching rate of the buffer layer is different 140 in the low density structural area A and the high density structural area B due to a difference in mask pattern densities. In other words, while the buffer layer 140 is etched down until the tops of the first mask structures 130 in the structural area B are exposed at high density, almost the entire buffer layer 140 removed when the distance d 2 of the first mask structures 130 is greater than twice the sum of an and b (ie d 2 > 2 (a + b)) in the low-density structural region A, as previously described above. As in 1G shown, the buffer layer 140 between two adjacent first mask structures 130 remain until the tops of the first mask structures 130 are exposed and the distance d 1 between the first mask structures 130 in the structure area A of low density is smaller than the sum of a and b (ie, [d 1 <a + b]), which similarly applies to the state of the high-density structure area B.
Referring to the 1H and 1I become the buffer layer 140 and the hardmask layer 124 between the first mask patterns 130 and the second mask patterns 150a are exposed using the first mask structures 130 and the second mask structures 150a etched as an etching mask to expose an upper surface of the etching film 120. For this purpose, first and second etching processes are carried out sequentially in a mutually different etching environment.
The following is the first etching process (see 1H ) and the second etching (see 1I ) of the buffer layer 140 and the hard mask layer 124 until the exposure of the top of the etching film 120 described in more detail. First referring to 1H For example, a dry etching process in the form of reactive ion etching (RIE) is used for the first etching, which is the buffer layer 140 and the hardmask layer 124 etched between the first mask patterns 130 and the second mask patterns 150a exposed, which are used as an etching mask.
If each of the buffer layer 140 and the hard mask layer 124 composed of an oxide-based material and the first mask patterns 130 and the second mask patterns 150a of polysilicon, a mixed gas of C x F y (where x and y are positive real numbers and preferably integers of 1 to 10), O 2 and Ar can be used as etchants for the first etching process. The C x F y gas may be C 4 F 6 or C 4 F 8 . In this case, an etch environment is achieved which is a production of polymer by-products 160 ( 1I ) is suppressed during the etching process until the tops of the etching film 120 are exposed in the structure area A with low density. In order to achieve the etching environment in which the production of the polymer by-products 160 is suppressed, a first flow rate ratio of a flow rate of O 2 gas to a flow rate of C x F y gas is set such that the first flow rate ratio has a relatively high flow rate of O 2 gas. For example, C x F y , O 2 and Ar may be supplied at a flow rate of 30 sccm, 55 sccm and 1000 sccm respectively during the first etching process. In this case, the first flow rate ratio of the flow rate of O 2 gas to the first flow rate of C x F y gas (ie, flow rate of O 2 gas: flow rate of C x F y gas) is 55:30. The first flow rate ratio of O 2 gas to the first flow rate of C x Fy gas is given as an example in the present embodiment. The invention is not limited to this flow rate ratio. The first flow rate ratio may vary according to the dimensions and densities of the structures and film quality. The first etching process may be carried out, for example, at room temperature.
In the present embodiment, when etching the buffer layer 140 and the hard mask layer 124 , as in 1G shown, a first thickness T 1 , the thickness of the hard mask layer 124 which remained, are etched in the structural area A at low density. In addition, the second thickness T 2 , which is a sum of the thicknesses of the hardmask layer, must be 120 and the buffer layer 140 is etched in the structural area B at high density, etched to the etching film 120 expose. Due to the different etching thicknesses in the low density structural area A and the high density structural area B, the hard mask layer becomes 124 completely etched to be the etch film first 120 in the structure area A of low density during the etching process of the hard mask layer 124 during the first Etching process in the structural area B was not completed with high density. Consequently, parts of the hard mask layer become 124 not etched, however, remain in the structural region B at high density until the top of the etching film 120 by continuous removal of the hard mask layer 124 is exposed in an area in which the distance d 2 between the first mask structures 130 is greater than twice the sum of a and b (ie, [d 2 > 2 (a + b)]). If the first etching is continued under these conditions, the etching film 120 also be over-etched in the structural area A with low density. Thus, the difference of the etching thicknesses T 1 and T 2 can be transferred to the low-density structural area A as it is. Therefore, to prevent the above-mentioned result, the first etching is stopped until the top of the etching film 120 is exposed in the structure area A with low density and in particular when the top of the etching film 120 is exposed in the region in which the distance d 2 between the first mask structures 130 is greater than twice the sum of a and b (ie, [d 2 > 2 (a + b)]).
Referring now to FIG 1I the second etching process is carried out in situ with the first etching process. In performing the second etching, the remaining portions of the remaining portions of the hardmask layer become 124 removed after the first etching process between the two adjacent first mask structures 130 or between the first mask structures 130 and the second mask structures 150a exist, so the tops of the etching film 120 between the first mask structures 130 and the second mask structures 150a in both the low density structural area A and the high density structural area B.
To the hard mask layer 124 etching until the top of the etching film 120 is exposed in the low-density structural region A and the high-density structural region B, a dry etching process involving inverse reactive ion etching (iRIE) retarding phenomena may be used. Consequently, the second etching is carried out under an etching environment in which the polymer by-products 160 that are generated are larger than in the first etching process. When performing the second etch that involves the iRIE delay phenomena, the polymer by-products accumulate 160 on the exposed top of the etch film 120 in the structural region A of low density because of the polymer by-products 160 can easily accumulate in an opening with a relatively small aspect ratio, ie, when the distance d 2 is greater than twice the sum of a and b. Thus, etching of the etching film 120 which is exposed in the structural region A of low density due to the polymer by-products 160 be prevented on the exposed top of the etching film 120 are accumulated in the structure area A with low density. While the polymer by-products 160 accumulated on the etching film 120 exposed in the structure area A of low density becomes the one between the first mask patterns 130 and the second mask structures 150a exposed hardmask layer 124 etched in the structural region B at a high density, whereby hard mask structures 124b are formed exposing the tops of the etching film 120. As a result, the top of the etching film 120 between the first mask structures 130 and the second mask structures 150a in the structural area B exposed at high density. When the etching is performed until the etching film 120 is exposed, the first mask structures 130 and the second mask patterns 150a used as an etching mask are partially or totally consumed as in FIG 1I shown.
When the hard mask layer 124 consists of an oxide-based material and the first mask structures 130 and the second mask structures 150a are each made of polysilicon, a mixed gas of C x F y , O 2 and Ar can be used as an etchant for the second etching process. The C x F y gas may be, for example, C 4 F 6 or C 4 F 8 . In this case, to perform the second etch in an etch environment in which the polymer by-products 160 larger than generated in the first etching process, the etchant having the same composition as used in the first etching, but the O 2 gas content of the etchant can be reduced. In other words, the etching environment of the second etching process is set at a second flow rate ratio in which the flow rate of O 2 gas is lower than that for the first etching process. For example, C x F y , O 2, and Ar may be supplied in the second etching process at a flow rate of 30sccm, 35sccm, and 1000sccm, respectively. In this case, the second flow rate ratio of the flow rate of O 2 gas to the flow rate of C x F y gas (ie, flow rate of O 2 gas: flow rate of C x F y gas) is 35:30. However, the second flow rate ratio described in the present embodiment is not limited to this ratio. The second flow rate ratio may be changed according to dimensions and densities of the structures, film quality, etc.
When the second etching process involving the iRIE delay phenomena is performed such that the second etching process is performed with the larger polymer by-products 160 Otherwise, the composition and flow rate ratio of the etchant for the second etch will be identical to those for the first etch however, an etch temperature may be about -5 ° C, which is lower than that of the first etch. In addition, it is possible for the second etching process to set the second flow rate ratio of the flow rate of O 2 gas to the flow rate of C x F y gas lower than that of the first etching process and simultaneously the etching temperature applied during the second etching process , lower than that of the first etching process.
Referring to 1y become the polymer by-products 160 removed, which have accumulated in the structure area A low density. Around the polymer by-products accumulated in the structural area A of low density 160 For example, a dry etching process in the form of a plasma process using a mixed gas of at least one gas selected from the group consisting of CHF 3 and CH 2 F 2 , O 2 and Ar may be used. Alternatively, to remove the polymer by-products accumulated in the low density structural region A, may be used 160 conventional incineration and stripping methods are used.
This will make the hardmask structures 124b showing the top of the etch film 120 in the structure area A of low density and the structure area B of high density. In this case, the hardmask structures exhibit 124b the width W 2 which is 1/4 of the second pitch 2P B , ie approximately equal to the first width W 1 of the first mask structures 130 in the high density structural area B, as shown. In addition, the hard mask structures exhibit 124b in the high-density pattern area B, the line and space patterns having the first pitch P B equal to one-half of the second pitch 2P B on the substrate 100 through the first mask structures 130 and the second mask structures 150a is. Furthermore, the hard mask structures have 124b a structural pattern repeated with the first pitch P A equal to the pitch P A of the first mask structures 130 is formed as with reference to 1B described, ie the first pitch P A of the structures, which ultimately on the etching film 120 should be formed in the structure area A with low density.
Referring to 1K becomes the etching film 120 using the hard mask structures 124b and the first mask structures 130 and the second mask structures 150a acting as an etching mask on the hardmask structures 124b are anisotropically dry etched to form the fine structures 120a.
In the structural area A of low density, the pattern transfer of the fine structures becomes 120a on the etching film 120 simply through the first mask structures 130 reached. However, in the high-density structure region B, the pattern transfer of the fine patterns 120a onto the etching film becomes 120 through the first mask structures 130 and the second mask structures 150a reached. Therefore, structures having a fine pitch which overcome resolution limitations of photolithography can be easily made in the high-density region B.
In addition, the hard mask layer 124 and the buffer layer 140 for structuring the hard mask layer 124 regardless of the thickness difference of the etching film 120 to be etched in the low density structural area A and the high density structural area B, as with reference to FIGS 1H and 1I etched by double etching using RIE and iRIE retardation effects, thereby alleviating the problems of differences in a structural profile corresponding to the pattern densities in the etch film structures 120a prevented after structuring of the etching film 120 to be obtained.
2 FIG. 12 is a graph illustrating a result of measuring an etching quantity of an oxide film according to the flow rate of O 2 of the etchant used for double etching using a RIE process and an iRIE delay process when the hard mask layer. FIG 124 is structured as with reference to the 1H and 1I described. To see the results of 2 In order to obtain the etching rate of an oxide film with respect to the flow rate of O 2 , when the oxide film filled between a plurality of polysilicon film structures was in a low-density structural area, with polysilicon film structures of a pitch of 65nm and a width of 40nm and in a structural area is etched at high density with the polysilicon film patterns having a pitch of 1 μm and a width of 120 nm using the polysilicon film patterns as an etching mask under an environment set such that a power supply Ws in an etching device for RIE 1200W was a bias power Wb 3500W was, the pressure was 20mT and a temperature was 20 ° C. The oxide film is formed by an ALD method. According to the results, a mixed gas of C 4 F 6 supplied at a flow rate of 30 sccm, Ar supplied at a flow rate of 1000 sccm and O 2 fed at different flow rates as in FIG 2 shown graphically, used as etchant of the oxide film.
After the result of 2 For example, both etching rates of the oxide film in both the low density structural region A and the high density structural region B were relatively high when the flow rate of O 2 was about 40 sccm or more. When the flow rate of O 2 was about 40 sccm or less, the etching rate of the oxide film in the high density structural area B was relatively high, but the oxide film was never etched in the low density structural area A. In other words, when the flow rate of O 2 was about 40 sccm or more, the amount of the polymer by-products generated under the etching environment was small to increase the oxide film in both the low density structural area A and the high density structural area B. etching. Meanwhile, when the flow rate of O 2 was about 40 sccm or less, the amount of generated polymer by-products increased 160 to, so that the polymer by-products 160 easily accumulated in the structure region A, and thus the oxide film was not etched.
A method of forming fine structures of a semiconductor device according to the invention uses double etching by varying an amount of generated polymer by-products to etch a film having a thickness which differs according to pattern densities in case the thicknesses in different regions increase etches, which have the different structural densities, differ from one another when structures having different dimensions with different grid dimensions are formed on a substrate using double structuring. In the double etching process performed to form the fine structures according to the invention, a first etching process involving RIE effects is performed in both a low-density structural region and a high-density structural region until an etching film is etched is uncovered by preventing the generation of polymer by-products. Then, a second etching process involving iRIE delay effects is performed by changing the etching environment to produce much polymer by-products until the surface of the etching film is exposed in the low-density structural region, and thus the polymer by-products accumulate the exposed etching film in the low density structural area, and a hard mask layer is etched in the high density structural area.
Therefore, in the method of forming the fine structures of the semiconductor device according to the invention, even if a film to be etched in regions having different pattern densities has different thicknesses, transfer of steps caused by the difference in thickness can be effectively prevented. As a result, structures having a fine pitch can be readily performed, overcoming the resolution limitations of photolithography.
A method of forming fine structures of a semiconductor device, comprising the steps of: forming a hard mask layer (124) in a first region (A) and a second region (B) of a substrate (100) including an etching film (120) to be etched Forming a plurality of mask patterns (130, 150a) and a buffer layer (140) on the hard mask layer (124), wherein the plurality of mask patterns (130, 150a) are repeatedly formed by forming a first pattern density in the first area (A ) and having a second pattern density greater than the first pattern density in the second region (B), and wherein the buffer layer (140) covers both sidewalls of the mask patterns (130, 150a) in the second region (B), first etching by reactive ion etching (RIE) of the buffer layer (140) and the hard mask layer (124) in both the first region (A) and the second region (B) under a first etch environment until it second surface for etching film (120) is exposed in the first region (A) using the mask patterns (130, 150a) as an etching mask, second etching for forming hard mask patterns (124b) under a state where the first surface of the etching film ( 120) is exposed in the first region (A) and the etching film (120) is not exposed in the second region (B) by etching the hard mask layer (124) until the second surface of the etching film (120) in the second region ( B), wherein a second etch environment is used to produce polymer byproducts (160) that accumulate on the first surface of the etch film (120) exposed in the first region (A), the mask structures (16). 130, 150a) are used as the etch mask and the first etch environment and the second etch environment are composed of identical etchant ingredients each containing O 2 and a flow rate of O 2 in the second etch environment g is smaller than the flow rate of O 2 in the first etching environment, removing the polymer byproducts (160) accumulated on the first surface to expose the first surface of the etching film (120), and forming etching film patterns (120a) by etching the exposed first surface and the second surface of the etching film (120) using the hard mask patterns (124b) as an etching mask.
Method according to Claim 1 wherein the second etch environment is selected to produce polymer byproducts that are larger and / or more numerous than in the first etch environment.
Method according to Claim 1 or 2 in which the buffer layer (140) is formed during the formation of the mask structures (130, 150a) and the buffer layer (140). both sidewalls of the mask patterns (130, 150a) are covered with widths of a and b in the second area (B), and a distance (d 2 ) between at least one pair of adjacent mask patterns in the first area (A) greater than 2 (a + b) is.
Method according to one of Claims 1 to 3 wherein a temperature of the second etching environment is lower than a temperature of the first etching environment.
Method according to one of Claims 1 to 4 in which - the buffer layer (140) and the hard mask layer (124) are formed by an oxide film, - the mask structures (130, 150a) are formed by a polysilicon film and - the first etching environment and the second etching environment are made of a mixed gas of C x F y (where x and y are integers between 1 and 10), O 2 and Ar are formed.
Method according to one of Claims 1 to 5 further comprising, after the first etch and before the second etch, changing the first etch environment to the second etch environment when the first surface of the etch film (120) is exposed, the flow rate of O 2 changing from the first etch environment to the second etch environment Etching environment is reduced, while other conditions of the first etching environment are initially held as in the first etching environment.
Method according to one of Claims 4 to 6 further comprising, after the first etch and before the second etch, changing the first etch environment to the second etch environment when the first surface of the etch film (120) is exposed, the etch temperature in the second etch environment changing to the first etch environment second etching environment is lowered to be lower than the etching temperature in the first etching environment, while other conditions of the first etching environment are originally maintained as in the first etching environment.
Method according to one of Claims 1 to 7 wherein a plasma dry etch process is used to remove the polymer by-products (160).
Method according to Claim 8 wherein a mixed gas having at least one gas selected from the group consisting of CHF 3 and CH 2 F 2 , O 2 and Ar is used to remove the polymer by-products (160) by the plasma desalting process.
Method according to one of Claims 1 to 7 wherein an ashing or debonding process is used to remove the polymer by-products (160).
Method according to one of Claims 1 to 10 wherein the first etching is performed under a state where the hard mask layer (124) is exposed between the mask patterns (130, 150a) in the first area (A) and the buffer layer (140) is sandwiched between the mask patterns (130, 150a) the second area (B) is exposed.
Method according to one of Claims 1 to 11 wherein the etching film (120) is made of a metal, a semiconductor or an insulating material.
Method according to one of Claims 1 to 12 wherein the mask structures (130, 150a) include first mask structures (130) formed in the first area (A) and the second area (B) and second mask structures (150a) that are only in the second area (B). and forming the mask patterns (130, 150a) and the buffer layer (140) comprises the steps of: forming the first mask patterns (130) repeated at a predetermined first pitch to be the first pattern density in the first area (A), and repeated with a second pitch to have a third pattern density in the second area (B) that is twice the second pattern density, forming the buffer layer (140) so as to form upper sides and side walls of the first one Covering mask patterns (130) and the top of the hardmask layer (124), and - forming the second mask patterns (150a) each between at least one pair of adjacent first masks structures (130) are located on the buffer layer (140) in the second region (B).
Method according to Claim 13 wherein the buffer layer (140) has an upper surface in which recesses are respectively formed between the two adjacent first mask patterns (130) and the second mask patterns (150a) are formed inside the recesses formed in the upper surface of the buffer layer (140) ,
Method according to Claim 13 or 14 wherein the second mask patterns (150a) are formed on a horizontal plane which is the same as that of the first mask patterns (130).
Method according to one of Claims 13 to 15 further comprising partially removing the buffer layer (140) after the formation of the second mask patterns (150a) to expose the tops of the first mask patterns (130).
Method according to one of Claims 13 to 16 further comprising, after forming the first mask patterns (130) and before forming the buffer layer (140), removing the hard mask layer (124) exposed between the first mask patterns (130) from the top of the hard mask layer (124) includes a first thickness to form lower surface portions on top of the hardmask layer (124).
Method according to Claim 17 wherein the first thickness is equal to a width of the first mask structures (130).
Method according to one of Claims 13 to 18 wherein each of the first mask patterns (130) has a width that is 1/4 of the second pitch.
Method according to one of Claims 13 to 19 wherein the first mask patterns (130) and the second mask patterns (150a) are formed by a polysilicon film, and the buffer layer (140) and the hard mask layer (124) are formed by an oxide film.
DE102008007671.6A 2007-02-06 2008-01-25 Process for forming fine structures of a semiconductor device Active DE102008007671B4 (en)
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KR1020070012347A KR100843236B1 (en) 2007-02-06 2007-02-06 Method of forming fine patterns of semiconductor device using double patterning process
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