JP2007243218A - Method of fabricating semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce accumulation of electric charges on a semiconductor device caused upon sputtering. <P>SOLUTION: The method of fabricating a semiconductor device includes the steps of: preparing a semiconductor wafer 140; forming an intermediate dielectric film 142 on the semiconductor wafer; sequentially forming a lower metal layer 146 and an interlayer insulating film 148 on the interlayer dielectric film; removing the intermediate insulating film corresponding to the edge region around the edge of the semiconductor wafer to expose an edge surface region 150 of the lower metal layer; forming an upper metal layer 152 by sputtering so as to cover the exposed edge surface region and the remaining interlayer insulating film; and forming a capacitor by patterning the interlayer insulating film and the upper metal layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device that reduces the influence of charges accumulated on a wafer by sputtering or dry etching.

  In general, in the wiring process after the gate is formed, there is a risk that Al, Ti, W, or the like of the wiring material may be oxidized by an oxidizing atmosphere or an interlayer insulating film when heat treatment is performed. Therefore, only heat of 400 ° C. or less is applied to prevent this oxidation. In order to perform etching at a processing temperature of about 400 ° C. or to deposit an insulating film while maintaining embeddability, the wafer is often exposed to a plasma atmosphere. In addition, it is exposed to a plasma atmosphere during metal sputtering. In these plasma atmospheres, accelerated ions and electrons collide with the wafer, and charges are injected into the wafer.

  In the case of a normal bulk wafer, most of the charges that have entered the wafer flow to the support substrate, so that the device is unlikely to be charged up. However, since an SOI wafer has a buried oxide film (also referred to as a BOX (Buried Oxide) oxide film) between the support substrate and the SOI layer on the wafer surface, the charge flowing from the wafer has a weak element insulation. Concentration of the electric field is caused at the location, and the reliability is lowered or the insulating film is destroyed.

  In the conventional semiconductor process, the gate insulating film is thinned with miniaturization. The gate electrode itself is insulated from the Si substrate through the gate insulating film, and if the charge due to the plasma atmosphere is accumulated during etching, the thin gate insulating film may be destroyed. For this reason, an apparatus used in gate etching or SW (Side Wall) etching has a mechanism in which charge is difficult to flow to the wafer. Further, if polysilicon is used as the gate material, high-temperature heat treatment is possible, so there is no plasma damage, and LP-CVD (Low Pressure Chemical Vapor Deposition) apparatus (film forming temperature: 700 to 800 ° C.) having excellent embeddability. Etc.) is generally used.

  As a method for preventing damage due to charge-up that occurs when forming an Al wiring, for example, in Patent Document 1, an exposed portion is provided on a silicon substrate on a grid line, and then a wiring pattern is formed across the grid line to form a substrate. A method of forming a current path that communicates has been proposed.

In addition, several methods have been proposed for controlling the substrate potential by providing a conduction path between the SOI layer insulated by the BOX oxide film 204 and the Si support substrate in the SOI wafer. Patent Document 2 proposes a method of forming a substrate contact in a buried oxide film that insulates the SOI layer side and the Si support substrate by forming a substrate contact. Patent Document 3 proposes a method of forming a short-circuit conductor for conducting the Si support substrate and the SOI layer in the vicinity of the scribe planned region. Patent Document 4 proposes a method in which a Si support substrate and an SOI layer on an upper portion of a buried oxide film are electrically connected by cutting along a scribe line.
JP-A-2-280321 JP 2001-177098 A JP-A-6-244239 JP 2002-164547 A

  LP-CVD, which is free from worrying about charging damage, is mainly used for interlayer insulating film deposition in the transistor formation process. On the other hand, recently, an AP-CVD (Atomospheric Pressure Chemical Vapor Deposition) apparatus which can be performed at a relatively low temperature has begun to be developed, but this apparatus has a problem in embedding. Also, in gate etching, dry etching is the mainstream, and an apparatus that prevents charges from being accumulated in a thin gate insulating film is used.

  However, in metal sputtering for wiring process after transistor formation and dry etching, charging damage due to the process is not considered much.

  FIG. 6 is a diagram schematically showing a state in which charges are accumulated by deposition of a metal layer by sputtering in a wiring process in a method of manufacturing a semiconductor device using an SOI wafer 200 by a partial cross-sectional cut. In the drawing, the left end corresponds to the wafer edge 222, and no semiconductor element is formed in the wafer edge region 224, which is a peripheral region from the wafer edge to the wafer center direction (here, about 5 mm) toward the wafer center. A region from the wafer center to the wafer edge region 224 is a device formation region, and various devices are formed here.

  Here, the SOI wafer 200 includes a Si support substrate 202, a BOX oxide film 204, and an SOI layer 206, and the Si support substrate 202 and the SOI layer 206 are insulated by a BOX oxide film 204 that is a buried oxide film. Individual devices formed on the SOI wafer 200 are separated by an element isolation region 208. In FIG. 6, detailed description is omitted, and the gate insulating film 210 and the gate electrode 212 are shown. An interlayer insulating film 214 is formed on the upper side of the SOI wafer 200 on which the device is formed, and a contact 216 for connecting to an upper wiring is formed on the gate electrode 212.

  A conductive layer 218 is formed by sputtering on the upper surface of the interlayer insulating film 214 and the contact 216 by patterning later to form a wiring. At this time, a charge on the wafer surface generated during sputtering (indicated by an arrow as charge injection 220 by sputtering) may accumulate in the device through the contact 216. These electric charges degrade a weakly insulating portion or cause dielectric breakdown. Since the electric charge accumulated in the device is insulated by the buried oxide film, there is no place to escape, and there is a possibility that stress more than the assumed electric field may be applied, thereby reducing the reliability of the device.

  A device formed by such a process results in an unstable yield due to generation of a leakage current due to dielectric breakdown or fluctuation of transistor characteristics.

  Therefore, the present invention prevents the decrease in device yield due to charge-up by reducing charge accumulation caused by metal sputtering or dry etching, which occurs when an insulating layer is embedded in the middle like an SOI wafer. With the goal.

  In order to solve the above-described problem, an edge region around the wafer that is not used for device formation, that is, a wafer edge region, is used for charge movement during sputtering. That is, according to the method of manufacturing a semiconductor device of the present invention, a step of preparing a semiconductor wafer, a step of forming an interlayer insulating film on the semiconductor wafer, and a lower metal layer and an intermediate insulating film are sequentially formed on the interlayer insulating film. And a step of exposing an edge surface region of the lower metal layer by removing an intermediate insulating film corresponding to an edge region around the semiconductor wafer (hereinafter simply referred to as a wafer edge region) by etching using a resist pattern. Forming an upper metal layer by sputtering so as to cover the exposed edge surface region and the remaining intermediate insulating film; and patterning the lower metal layer, the intermediate insulating film, and the upper metal layer to form a capacitor. And a forming step.

  Here, the wafer edge region is a region around the wafer edge from the wafer edge to the center of the wafer up to about 5 mm when viewed from the front side, and is a region that is not normally used for device formation.

  According to the method for manufacturing a semiconductor device of the present invention, since the conductive layer deposited by sputtering is in contact with the support, charges generated during the sputtering can be released to the support. As a result, deterioration of the insulating film can be suppressed, and a device can be formed on the wafer without impairing reliability.

  In addition, the area on the surface of the support substrate of about 5 mm from the wafer edge used for connecting the Si support substrate and the conductive layer to the wafer center side is an area that cannot be used as a device from the beginning, so that etching does not affect the yield. .

  Hereinafter, a reference example and the best mode for carrying out the present invention will be described with reference to the drawings. In addition, each figure explaining a manufacturing method has shown schematically the cross-sectional cut end of the structure obtained in each step of a manufacturing process. Further, the size, shape, and arrangement relationship of each component constituting the structure are schematically shown to such an extent that the present invention can be understood. Moreover, in each figure, the same component is shown with the same number, and the overlapping description may be omitted.

<Reference example>
A method for manufacturing a semiconductor device of a reference example will be described with reference to FIGS. In this reference example, a process of forming a wiring on an SOI wafer is shown as an example. Here, for example, a Si support substrate 102 made of a semiconductor material is used as a support, an intermediate insulating layer is, for example, a BOX oxide film 104, and a conductive layer is sequentially stacked as a conductive layer formed by sputtering. 100 will be described as an example.

  FIG. 1A shows a stage in the process of manufacturing a semiconductor device on an SOI wafer. An interlayer insulating film 108 is stacked on the upper surface of the SOI wafer 100 in which the Si support substrate 102, the BOX oxide film 104, and the SOI layer 106 are sequentially stacked (FIG. 1A). 1 and 2, the left end portion is a wafer edge 112, and although the description is omitted here in the SOI layer 106 and the interlayer insulating film 108 in the device formation region 116, the element isolation region and the gate insulating film are omitted. A semiconductor element including a gate electrode and a contact is formed.

  Next, a resist film 110 is applied on the upper surface of the interlayer insulating film 108. As the resist film 110, a positive resist is used. The positive resist is peripherally exposed to remove the resist film portion of the wafer edge region 114. Only the resist edge region corresponding to the wafer edge region 114 of the resist film 110 is exposed by the peripheral exposure 118 (FIG. 1B). In normal photolithographic etching, the exposure location is limited using a mask pattern. Here, the exposure is performed without using the mask pattern by the peripheral exposure function of the exposure apparatus.

  The peripheral exposure function of the exposure apparatus is a function for performing exposure only on the peripheral portion of the wafer, that is, the wafer edge region in this embodiment. Although it is not a function that is normally installed in a general exposure apparatus, for example, a peripheral exposure function can be installed as an additional function in an exposure apparatus manufactured by Tokyo Electron Limited.

  A resist pattern 110a can be formed by performing development processing after the peripheral exposure (FIG. 1C). 3A and 3B schematically show the entire wafer on which the resist pattern 110a is formed. FIG. 3A is a plan view of the formed resist pattern 110a viewed from the upper side of the wafer. FIG. 3B is a cross-sectional view taken along the broken line XX in FIG.

  Next, using the resist pattern 110a as a mask, dry etching is performed on the exposed layer portion of the interlayer insulating film 108 and the wafer edge region of the SOI wafer 100 below the interlayer insulating film 108 to form the edge surface region 120 of the Si support substrate 102. Expose (FIG. 1D).

  Next, the resist pattern 110a is removed, and sputtering is performed so as to cover the exposed edge surface region 120 and the remaining BOX oxide film 104, which is an intermediate insulating layer, from above by exposing the conductive layer 122 to be a wiring in a later process. (FIG. 2A). Here, the conductive layer 122 is formed so as to cover the entire upper surface of the remaining wafer 100. That is, the conductive layer 122 is formed without interruption from the upper surface of the interlayer insulating film 108 through the side surface to the exposed surface of the Si support substrate 102.

  Next, the conductive layer 122 is patterned on the wiring 122a by a known photolithography / etching technique (FIG. 2B).

  FIG. 4 is a diagram for explaining the movement of charges during sputtering in this reference example. An element isolation region 124 formed in the SOI layer 106, a gate insulating film 126, a gate electrode 128, and a contact 130, which are omitted in the explanatory diagram of the manufacturing process, are also shown. In the conventional formation of the conductive layer by sputtering shown in FIG. 6, since the conduction to the Si support substrate is interrupted by the BOX oxide film, the charge by the sputtering is accumulated. On the other hand, in this reference example, the conductive layer 122 is formed by sputtering after the surface of the wafer edge region of the Si support substrate 102 is exposed. Accordingly, the charge accumulated in the conductive layer 122 by the charge injection 132 by sputtering flows, that is, moves from the edge surface region 120 in contact with the conductive layer 122 of the Si support substrate 102 to the Si support substrate 102. No charge is accumulated in the. Therefore, it is possible to prevent problems such as dielectric breakdown of the gate insulating film that occur in the device.

  In addition, the electric charge generated during the dry etching in the patterning process of the wiring 122a can be released to the Si support substrate 102 because the conductive layer 122 is connected to the Si support substrate 102 up to an intermediate stage. is there. Therefore, charge accumulation can be reduced even in this etching step, compared to the conventional manufacturing method.

  In this reference example, the peripheral exposure function of the exposure apparatus was used to form the resist pattern 110a excluding the resist edge region of the resist film in the wafer edge region. As a method of forming the resist pattern 110a, a spin coater used for applying a resist film can also be used.

  Generally, a spin coater has a function of dropping a chemical solution only on a wafer edge region to remove a resist. Therefore, after the resist film 110 is applied by a spin coater, the resist film portion in the resist edge region is dissolved and removed by a chemical solution, and then the entire resist film is exposed. In this case, in order to form the exposed portion of the resist film as the resist pattern 110a, a negative resist is used as the resist film material. For example, PGMEA (propylene glycol monomethyl ether acetate) is used as the chemical solution for removing the resist film. By performing development after exposure, a resist pattern 110a can be formed on the wafer surface excluding the wafer edge region.

  Further, in FIG. 3, the shape of the wafer is simplified, and is represented by a circle when viewed from above the wafer. Actually, in general wafers, cut portions such as OF (orientation flat) and notches are formed. Since a wafer with an OF has a portion in which the wafer edge is linear when viewed in plan from the wafer surface, the chemical solution may not be successfully dropped onto the resist film when the resist in the wafer edge region is removed with a spin coater. . Therefore, in the case of a wafer provided with OF, it is more preferable to form the resist pattern 110a using the peripheral exposure function.

  When this reference example is applied to a multilayer wiring, if the step of exposing the surface of the support in the wafer edge region is performed every time before the wiring conductive layer for each layer is sputtered, the conductive layer for wiring is supported by the support. Therefore, accumulation of electric charge due to sputtering can be prevented.

  As described above, according to this reference example, in the wiring process when the semiconductor device is formed on the SOI wafer, the edge surface region corresponding to the wafer edge region of the Si support substrate 102 is exposed, and then the conductivity by sputtering. Since the layer 122 is formed, charges can move from the edge surface region 120 of the Si support substrate 102 in contact with the conductive layer 122 to the Si support substrate 102. Therefore, no charge is accumulated in the device, and it is possible to reduce problems such as dielectric breakdown, and it is possible to prevent a decrease in device yield due to charge-up.

<Embodiment>
The present invention can be applied to a process of sputtering on an upper portion of an insulator layer formed on a support made of a semiconductor material or a conductor material. In the reference example described above, an example of wiring formation of a semiconductor element formed on an SOI wafer whose support is formed of a semiconductor material has been described. On the other hand, in this embodiment, a case will be described in which a capacitor having a MIM (Metal-Insulator-Metal) structure in which the support is made of a conductive material is formed.

  With reference to FIG. 5, an example in which a capacitor having an MIM structure is formed on the Si wafer 140 will be described. Here, an example will be described in which the support is a lower metal layer 146 made of a conductive material, the insulating layer is an intermediate insulating film 148, and the conductive layer is an upper metal layer 152 formed by sputtering.

  An interlayer insulating film 142 is formed on the entire upper surface of the Si wafer 140, and a contact 144 for conducting a capacitor (not shown) formed in a later process is formed.

  A lower metal layer 146 is formed as a support on the interlayer insulating film 142 by sputtering. In this sputtering, since charges can move to the Si wafer 140 through the contact 144, there is no need to consider a problem due to charge accumulation.

  Next, an intermediate insulating film 148 is formed over the entire upper surface of the lower metal layer 146 (FIG. 5A).

  Similar to the reference example already described, a resist pattern (not shown) is formed only in the device formation region 116 excluding the wafer edge region 114. By dry etching, the layer portion of the intermediate insulating layer 148 exposed from the resist pattern is removed by etching to expose the edge surface region 150 of the lower metal layer 146. Thereafter, the resist pattern is removed (FIG. 5B).

  Next, the upper metal layer 152 is formed on the entire upper surface of the remaining wafer over the edge surface region 150 of the lower metal layer 146 exposed from the intermediate insulating film 148 by sputtering. During this sputtering, charge moves to the lower metal layer 146 side through the exposed edge surface region 150 of the lower metal layer 146, so that charge accumulation due to sputtering can be prevented (FIG. 5C). ).

  Next, the MIM structure capacitor can be formed by patterning the lower metal layer 146, the intermediate insulating film 148, and the upper metal layer 152 by a known photolithography etching technique (not shown).

  As described above, by the insulating layer formed on the support, which is a conductive material, the charge accumulated when the conductive layer is sputtered on the upper side of the insulating layer is exposed to the support by exposing the surface of the support by etching. Can move. As a result, problems caused by charge accumulation can be reduced, and a reduction in device yield can be prevented.

  The support surface exposed before the sputtering of the conductive layer is not necessarily performed on the entire circumference of the wafer edge region, but is formed by peripheral exposure or resist film peeling on the wafer edge region as in the above-described embodiment. In the case of using a resist pattern, it is preferable to expose the support surface in the wafer edge region over the entire circumference of the wafer because the operation is simple.

  In addition, if the area where the surface of the support is exposed, that is, the edge surface area, is the entire area except for the area where the device is formed (patterned), the outside of the device formed on the outermost periphery. In addition, a step corresponding to the film thickness of the film removed by etching occurs. When forming a pattern on a submicron scale, if there is such a step on the wafer surface, a pattern abnormality due to defocusing occurs around the surface, which may reduce the yield of the outermost device. Therefore, it is preferable that the region where the surface of the support is exposed be a peripheral region from the wafer edge to the wafer center of about 5 mm, that is, the wafer edge region.

(A)-(D) are process drawings for demonstrating the manufacturing method of the semiconductor device of a reference example. (A) And (B) is process drawing following the process of FIG.1 (D). (A) And (B) is a figure for showing the structure of a resist pattern. It is a figure for demonstrating the movement of the electric charge during sputtering. (A)-(C) are process drawings for demonstrating the manufacturing method of the semiconductor device of embodiment of this invention. It is a figure for demonstrating the manufacturing process of the conventional semiconductor device.

Explanation of symbols

100, 200: SOI wafer 102, 202: Si support substrate 104, 204: BOX oxide film 106, 206: SOI layer 108, 142, 214: Interlayer insulating film 110: Resist film 110a: Resist pattern 112, 222: Wafer edge 114, 224: Wafer edge region 116, 226: Device formation region 118: Peripheral exposure 120, 150: Edge surface region 122, 218: Conductive layer 122a: Wiring 124, 208: Inter-element isolation region 126, 210: Gate insulating film 128, 212: Gate electrodes 130, 144, 216: Contacts 132, 220: Charge injection by sputtering 140: Si wafer 146: Lower metal layer 148: Intermediate insulating film 152: Upper metal layer

Claims (3)

A step of preparing a semiconductor wafer;
Forming an interlayer insulating film on the semiconductor wafer;
A step of sequentially forming a lower metal layer and an intermediate insulating film on the interlayer insulating film;
Removing the intermediate insulating film corresponding to the wafer edge region of the semiconductor wafer by etching using a resist pattern to expose the edge surface region of the lower metal layer;
Forming an upper metal layer by sputtering so as to cover the exposed edge surface region and the remaining intermediate insulating film;
Forming a capacitor by patterning the lower metal layer, the intermediate insulating film, and the upper metal layer. In the manufacturing method of the semiconductor device according to claim 1,
The step of forming the resist pattern is a pre-step of the step of exposing the edge surface region,
Forming a resist film over the entire upper surface of the intermediate insulating film;
A step of performing peripheral exposure on the resist edge region of the resist film corresponding to the wafer edge region using a peripheral exposure function of an exposure apparatus;
And a step of removing a resist edge region of the resist film which has been peripherally exposed. In the manufacturing method of the semiconductor device according to claim 1,
The step of forming the resist pattern is a pre-step of the step of exposing the edge surface region,
Forming a resist film over the entire upper surface of the intermediate insulating film;
Removing the resist edge region of the resist film corresponding to the wafer edge region by applying a chemical solution to the upper surface of the resist film using a spin coater;
And a step of exposing the remaining resist film.

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