阅读说明：本技术 测试阵列结构、晶圆结构与晶圆测试方法 (Test array structure, wafer structure and wafer test method ) 是由 杨仓博 饶瑞修 于 2020-08-14 设计创作，主要内容包括：本发明公开了一种测试阵列结构、晶圆结构与晶圆测试方法,测试阵列结构包括基板、第一胞、第二胞、第一与第二位线环以及四个字线。第一与第二胞中的每一个都具有依序排列且彼此连接在一起的第一漏极区、第一栅极区、源极区、第二栅极区以及第二漏极区。第一胞的第一漏极区与第一栅极区位于第一位线环内。第一胞的第二栅极区以及第二漏极区位于第一位线环与第二位线环之间。第二胞的第一漏极区与第一栅极区位于第二位线环内。第二胞的第二栅极区以及第二漏极区位于第一与第二位线环之外。第一胞的第二漏极区与第二胞的第一漏极区位于其中二个彼此最相邻的字线之间。借此,能够测试晶圆结构在二个不同方向上的电流泄漏,从而确认晶圆结构的品质。(The invention discloses a test array structure, a wafer structure and a wafer test method. Each of the first and second cells has a first drain region, a first gate region, a source region, a second gate region, and a second drain region arranged in sequence and connected to each other. The first drain region and the first gate region of the first cell are located within the first bit line ring. The second gate region and the second drain region of the first cell are located between the first bitline ring and the second bitline ring. The first drain region and the first gate region of the second cell are located within the second bit line ring. The second gate region and the second drain region of the second cell are located outside the first and second bitline loops. The second drain region of the first cell and the first drain region of the second cell are located between two of the word lines that are most adjacent to each other. Therefore, the current leakage of the wafer structure in two different directions can be tested, and the quality of the wafer structure can be confirmed.)

1. A test array structure, comprising:

a substrate;

a first cell and a second cell, wherein each of the first and second cells has a first drain region, a first gate region, a source region, a second gate region, and a second drain region arranged in sequence and connected together;

a first bitline ring and a second bitline ring on the substrate, wherein the first drain region and the first gate region of the first cell are located within the first bitline ring, the second gate region and the second drain region of the first cell are located between the first bitline ring and the second bitline ring, the first drain region and the first gate region of the second cell are located within the second bitline ring, and the second gate region and the second drain region of the second cell are located outside the first and second bitline rings; and

a first word line, a second word line, a third word line and a fourth word line located over the first and second bitline loops, wherein the second drain region of the first cell and the first drain region of the second cell are located between the second and third word lines.

2. The test array structure of claim 1, wherein each of the first and second bitline loops is a closed elliptical loop extending in a first direction.

3. The test array structure of claim 2, wherein the first, second, third, and fourth word lines are parallel to each other and extend in a second direction perpendicular to the first direction.

4. The test array structure of claim 1, further comprising:

a plurality of capacitors, wherein each of the plurality of first and second drain regions is respectively connected to a corresponding capacitor of the plurality of capacitors.

5. The test array structure of claim 1, wherein the source region of the first cell is located below the first bitline ring and connected to the first bitline ring, and the source region of the second cell is located below the second bitline ring and connected to the second bitline ring.

6. The test array structure of claim 1, wherein the first gate region of the first cell is under the first word line and connected to the first word line, the second gate region of the first cell is under the second word line and connected to the second word line, the first gate region of the second cell is under the third word line and connected to the third word line, and the second gate region of the second cell is under the second word line and connected to the fourth word line.

7. The test array structure of claim 1, further comprising:

a third cell having a first drain region, a first gate region, a source region, a second gate region, and a second drain region arranged in sequence and connected together, wherein the first drain region and the first gate region of the third cell are located between the first and second bitline loops, and the second gate region and the second drain region of the third cell are located within the second bitline loop.

8. The test array structure of claim 1, wherein each of the first cell and the second cell has a channel region, the channel regions in the first cell and the second cell being located under the respective first and second gate regions in the first cell and the second cell, respectively.

9. A wafer structure comprising a plurality of wafers, wherein at least one of the plurality of wafers has the test array structure of claim 1.

10. A wafer testing method, comprising:

providing a wafer structure having the test array structure of claim 1;

applying an opening voltage to the first bitline loop and applying a closing voltage to the second bitline loop;

applying a turn-on voltage to the first, second, third, and fourth word lines, respectively, and measuring a first leakage magnitude, wherein the first leakage magnitude is a current between the second drain region of the first cell and the first drain region of the second cell;

applying a turn-off voltage to the first and third word lines, applying a turn-on voltage to the second and fourth word lines, and measuring a second leakage magnitude, wherein the second leakage magnitude is a current between the second drain region of the first cell and the first drain region of the second cell;

comparing the first leakage amplitude with the second leakage amplitude to judge whether current leakage occurs between the first cell and the second cell; and

and if the current leakage occurs between the first cell and the second cell, marking the wafer structure as a damaged wafer.

11. The wafer testing method of claim 10, wherein the test array structure further comprises a third cell having a first drain region, a first gate region, a source region, a second gate region, and a second drain region arranged in sequence and connected together, wherein the first drain region and the first gate region of the third cell are located between the first and second bitline rings, and the second gate region and the second drain region of the third cell are located within the second bitline ring, the wafer testing method further comprising:

measuring a third leakage magnitude, wherein the third leakage magnitude is a current between the second drain region of the first cell and the first drain region of the third cell;

judging whether another current leakage occurs between the first cell and the third cell according to the magnitude of the third leakage amplitude; and

if the other current leakage occurs between the first cell and the third cell, marking the wafer structure as a damaged wafer.

Technical Field

The invention relates to a test array structure, a wafer structure and a wafer test method.

Background

For the fabrication of semiconductor devices, it is an important issue to determine the quality of a wafer. Thus, a variety of different electrical parameter tests can be performed on the wafer. For the wafer to be tested, a test chip can be disposed on the wafer to be tested, and the engineer can confirm the quality of the wafer to be tested by measuring the electrical characteristics of the test chip.

The test wafer may be a mini array Test Element Group (TEG). However, it is difficult for the conventional array test element group having the container to test whether or not a current leakage occurs in two directions perpendicular to each other.

Disclosure of Invention

To achieve the above objectives, some embodiments of the present invention relate to a test array structure, a wafer structure and a wafer test method.

One embodiment of the invention relates to a test array structure. The test array structure comprises a substrate, a first cell, a second cell, a first bit line ring and a second bit line ring which are positioned on the substrate, and a first word line, a second word line, a third word line and a fourth word line which are positioned above the first bit line ring and the second bit line ring. Each of the first and second cells has a first drain region, a first gate region, a source region, a second gate region, and a second drain region arranged in sequence and connected together. The first drain region and the first gate region of the first cell are located within the first bit line ring. The second gate region and the second drain region of the first cell are located between the first bitline ring and the second bitline ring. The first drain region and the first gate region of the second cell are located within the second bit line ring. The second gate region and the second drain region of the second cell are located outside the first and second bitline loops. The second drain region of the first cell and the first drain region of the second cell are located between the second and third word lines.

In one or more embodiments, each of the first and second rings of bitwires is a closed elliptical ring extending in the first direction.

In some embodiments, the first, second, third and fourth word lines are parallel to each other and extend in a second direction perpendicular to the first direction.

In one or more embodiments, the test array structure as described above further comprises a plurality of capacitors. Each of the first and second drain regions is connected to a corresponding one of the capacitors.

In one or more embodiments, the source region of the first cell is located below and connected to the first bitline ring. The source region of the second cell is located below the second bitline ring and connected to the second bitline ring.

In one or more embodiments, the first gate region of the first cell is located under and connected to the first word line. The second gate region of the first cell is located under and connected to the second word line. The first gate region of the second cell is located under and connected to the third word line. The second gate region of the second cell is located under the second word line and is connected to the fourth word line.

In one or more embodiments, the test array structure as described above further comprises a third cell. The third cell has a first drain region, a first gate region, a source region, a second gate region, and a second drain region arranged in sequence and connected together. The first drain region and the first gate region of the third cell are located between the first and second bitline loops. The second gate region and the second drain region of the third cell are located within the second bitline loop.

In one or more embodiments, each of the first cell and the second cell has a channel region. The channel regions of the first cell and the second cell are respectively positioned under the corresponding first gate region and the second gate region in the first cell and the second cell.

Another embodiment of the invention relates to a wafer structure. The wafer structure includes a plurality of chips, and at least one of the chips has the test array structure as described above.

Another embodiment of the invention relates to a wafer testing method. The wafer testing method comprises the following procedures. An opening voltage is applied to the first bitline ring, and a closing voltage is applied to the second bitline ring. Applying a turn-on voltage to the first, second, third, and fourth word lines, respectively, and measuring a first leakage magnitude, wherein the first leakage magnitude is a current between the second drain region of the first cell and the first drain region of the second cell. Applying a turn-off voltage to the first and third word lines, applying a turn-on voltage to the second and fourth word lines, and measuring a second leakage magnitude, wherein the second leakage magnitude is a current between the second drain region of the first cell and the first drain region of the second cell. Comparing the first leakage amplitude with the second leakage amplitude to determine whether current leakage occurs between the first cell and the second cell. If the current leakage occurs between the first cell and the second cell, the wafer structure is marked as a damaged wafer.

In one or more embodiments, the test array structure further comprises a third cell. The third cell has a first drain region, a first gate region, a source region, a second gate region, and a second drain region arranged in sequence and connected together. The first drain region and the first gate region of the third cell are located between the first and second bitline loops. The second gate region and the second drain region of the third cell are located within the second bitline loop. And the wafer testing method further comprises the following procedures. A third leakage magnitude is measured, where the third leakage magnitude is a current between the second drain region of the first cell and the first drain region of the third cell. And judging whether current leakage occurs between the first cell and the third cell according to the magnitude of the third leakage amplitude. If the current leakage occurs between the first cell and the third cell, the wafer structure is marked as a damaged wafer.

In summary, the test array structure of the present invention can include two horizontal bit line rings and a plurality of vertical word lines, and can perform a current leakage test in two vertical and horizontal directions perpendicular to each other. The test array structure can be provided on a wafer structure under test so that the quality of the wafer structure under test can be confirmed.

The foregoing is merely illustrative of the problems to be solved, solutions to problems, and effects produced by the present invention, and specific details thereof are set forth in the following description and the related drawings.

Drawings

The advantages of the invention, together with the accompanying drawings, will be best understood from the following description taken in connection with the accompanying drawings. The description of the figures is for illustrative embodiments only and is not intended to limit individual embodiments or the scope of the claims.

FIG. 1A shows a top view of a test array structure according to one embodiment of the present invention;

FIGS. 1B and 1C are schematic top views of a test array structure according to one embodiment of the present invention;

FIGS. 2, 3 and 4 are cross-sectional views of different cells in the test array structure of FIG. 1A, respectively;

FIG. 5 illustrates a cross-sectional view of FIG. 1B taken along line C1-C1';

FIG. 6 illustrates a cross-sectional view of FIG. 1C taken along line C2-C2';

FIG. 7 shows a schematic top view of a wafer structure, according to an embodiment of the invention;

FIG. 8 is a flow chart of a wafer testing method according to one embodiment of the present invention;

FIG. 9 is a graph showing voltage relationships for different regions of a test array structure during different flows of a wafer test method;

FIG. 10 is a graph depicting leakage magnitude at various locations in a test array structure; and

FIG. 11 is a flowchart illustrating a process of the wafer testing method shown in FIG. 8.

Description of the main reference numerals:

100-testing the array structure; 110-a substrate; 120-a first cell; 122, 130-drain region; 123,131-drain terminal; 124, 128-gate region; 126-source region; 132-a channel region; 140-a second cell; 142,150-drain region; 143,151-drain terminal; 144, 148-gate region; 146-a source region; 152-a channel region; 160-third cell; 162, 170-drain region; 163,171-drain terminal; 164, 168-gate region; 166-a source region; 172-channel region; 200-a wafer structure; 210-a wafer; 300-wafer test method; 310-390-procedure; BLR1, BLR2, BLR 3-bit wire loop; WL1, WL2, WL3, WL4, WL5, WL6, WL 7-word line; C1-C1' -segment; C2-C2' -segment; IA-isolation region.

Detailed Description

The following detailed description is provided by way of example only and is not intended to limit the scope of the present invention, which is defined by the claims, and the description of the illustrated embodiments is not intended to limit the scope of the invention. In addition, the drawings are for illustrative purposes only and are not drawn to scale. For ease of understanding, the same or similar elements will be described with the same reference numerals in the following description.

Also, the terms (terms) used throughout the specification and claims have the ordinary meaning as is accorded to each term used in this field, in this disclosure and in the claims, unless otherwise indicated. Certain terms used to describe the invention are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the invention.

In this document, the terms "first", "second", and the like are used only for distinguishing elements or operation methods having the same technical terms, and are not intended to indicate a sequence or limit the present invention.

Furthermore, the terms "comprising," "including," "providing," and the like, are intended to be open-ended terms that mean including, but not limited to.

Further, in this document, the terms "a" and "an" may be used broadly to refer to a single or to a plurality of such terms, unless the context specifically states otherwise. It will be further understood that the terms "comprises," "comprising," "includes," "including," "has," "having," and similar language, when used herein, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Please refer to fig. 1A. FIG. 1A shows a top view of a test array structure 100 according to one embodiment of the present invention. As shown, the test array structure 100 includes a substrate 110, a bit line ring BLR1, a bit line ring BLR2, a bit line ring BLR3, a word line WL1, a word line WL2, a word line WL3, a word line WL4, a word line WL5, a word line WL6, a word line WL7, and a plurality of cells (cells). These cells are similar to memory cells in a memory. In the present embodiment, the cells are formed in the substrate 110 and include a first cell 120, a second cell 140, and a third cell 160. The drain terminals (shown as circles on the substrate 110, see below) of the first cell 120, the second cell 140, and the third cell 160 are located on the substrate 110. In fig. 1A, a word line WL1, a word line WL2, a word line WL3, a word line WL4, a word line WL5, a word line WL6, and a word line WL7 are arranged in this order.

In the present embodiment, each of the first cell 120, the second cell 140 and the third cell 160 is composed of two metal-oxide-semiconductor field-effect transistors (MOSFETs). Each of the first cell 120, the second cell 140, and the third cell 160 has two drain regions, two gate regions, a common source region, and a channel region formed in the substrate 110. The channel regions of the first cell 120, the second cell 140, and the third cell 160 are respectively located under the corresponding first and second gate regions of the first cell 120, the second cell 140, and the third cell 160. Isolation regions may be established between the two cells to electrically isolate each cell from the other cell. The circles on the substrate 110 in fig. 1A are the drain terminals of a plurality of cells, such as the first cell 120, the second cell 140, and the third cell 160. The drain terminals are connected to drain regions of a plurality of cells, such as the first cell 120, the second cell 140, and the third cell 160, respectively. For further details, please refer to the following discussion.

As shown in fig. 1A, from top to bottom, the (first) bitline ring BLR1, the (second) bitline ring BLR2, and the (third) bitline ring BLR3 are closed elliptical rings that extend along the x-axis direction and are arranged in parallel along the y-axis direction. The bit line rings BLR1, BLR2, and BLR3 may be made of a conductive material and connected to the first cell 120, the second cell 140, and the third cell 160. In fig. 1A, a portion of the drain terminals of the cells (e.g., the first cell 120, the second cell 140, and the third cell 160) are located within the bitline rings BLR1, BLR2, and BLR3, and a portion of the drain terminals are located between the bitline rings BLR1, BLR2, and BLR 3.

Word lines WL1-WL7 are formed over bit line loops BLR1, BLR2, and BLR 3. Word lines WL1-WL7 are not directly electrically connected to bit line rings BLR1, BLR2 and BLR 3. In this embodiment, word lines WL1-WL7 extend along the y-axis direction, which is perpendicular to the x-axis direction along which bit line rings BLR1, BLR2 and BLR3 extend. The word lines WL1-WL7 are used to connect to gate regions of cells (e.g., the first cell 120, the second cell 140, and the third cell 160), and the word lines WL1-WL7 can be used to control MOSFETs within the cell. In some embodiments, the extension direction of the bit line loop is staggered with respect to the extension direction of the word line.

In fig. 1A, cells (e.g., first cell 120, second cell 140, and third cell 160) are arranged to form a cell array. The bit line loops BLR1, BLR2, and BLR3 surround portions of the drain terminal. Word lines WL1-WL7 are further formed over bit line loops BLR1, BLR2, and BLR 3. The drain terminals of the cells are each located between bitline loops (e.g., within one of bitline loops BLR1, BLR2, and BLR3, or between bitline loops BLR1, BLR2, and BLR3) and between wordline WL1-WL 7. The bit line loops BLR1, BLR2, BLR3 and the word lines WL1-WL7 form rectangular areas, and drain terminals of cells (e.g., the first cell 120, the second cell 140, and the third cell 160) are respectively located in the rectangular areas. In some embodiments, the drain terminal may be a capacitor, and each cell may be one of the memory cells of the memory.

For simplicity, please refer to fig. 1B and fig. 1C. Fig. 1B and 1C show schematic top views of a test array structure 100 according to an embodiment of the invention. In fig. 1B and 1C, only three cells, i.e., the first cell 120, the second cell 140, and the third cell 160, are shown on the substrate 110.

In fig. 1B, the first cell 120 and the second cell 140 are labeled as two nearest neighbor cells. In the test array structure 100, current leakage between the first cell 120 and the second cell 140 can be measured.

FIG. 2 is a cross-sectional view of the first cell 120 in the test array structure 100 of FIG. 1A. The first cell 120 includes a drain region 122, a gate region 124, a source region 126, a gate region 128, and a drain region 130. Each of the gate regions 124 and 128 is formed by a semiconductor region and an insulating region surrounding the semiconductor region. In the cross-section provided in fig. 2, it can be considered that (first) drain region 122, (first) gate region 124, source region 126, (second) gate region 128, and (second) drain region 130 are arranged and connected together in sequence from left to right. Channel region 132 is located under gate region 124 and gate region 128. Isolation regions IA are formed on both sides of the first cell 120 to electrically isolate the first cell 120 from other cells on the substrate 110.

In the first cell 120, the drain region 122, the gate region 124, and the source region 126 form one MOSFET, the drain region 130, the gate region 128, and the source region 126 form another MOSFET, and the two MOSFETs share one source region 126. In one embodiment, the two MOSFETs in each cell include two p-type MOSFETs. In some embodiments, the two MOSFETs in each cell may also be two n-type MOSFETs.

In fig. 2, the first cell 120 further includes a drain terminal 123 and a drain terminal 131. Drain terminals 123 and 131 are connected to drain regions 122 and 130, respectively. The drain terminal 123 and the drain terminal 131 may be conductive materials. In some embodiments, the drain terminals 123 and 131 may include capacitors, such that the first cell 120 may be a Dynamic Random Access Memory (DRAM) cell composed of two 1T1C (one-capacitor) Memory cells. Similarly, in some embodiments, the second cell 140 and the third cell 160 may also be similar memory cells. In other words, the first cell 120, the second cell 140 and the third cell 160 can be formed by a DRAM memory process.

As shown in fig. 2, the bit line ring BLR1 is located on the source region 126 of the first cell 120. The bit line ring BLR1 is electrically connected to the source region 126. Two nearest neighboring word lines WL3 and WL4 are connected to gate region 124 and gate region 128, respectively. Referring to fig. 1A and 2, the extending direction (x-axis direction) of the bit line ring BLR1 and the extending direction (y-axis direction) of the word line WL3 and the word line WL4 are substantially perpendicular to each other. The bitline ring BLR3 crosses the wordline WL3 and the wordline WL 4.

Similarly, please refer to fig. 3. FIG. 3 is a cross-sectional view of a second cell 140 of the test array structure 100 of FIG. 1A. The second cell 140 includes a drain region 142, a gate region 144, a source region 146, a gate region 148, and a drain region 150. Each of the gate regions 144 and 148 is formed by a semiconductor region and an insulating region surrounding the semiconductor region. In the cross-section provided in fig. 3, it can be considered that the (first) drain region 142, the (first) gate region 144, the source region 146, the (second) gate region 148, and the (second) drain region 150 are arranged and connected together in sequence from left to right. The channel region 152 is located below the gate regions 144 and 148. Isolation regions IA are formed on both sides of the second cell 140 to electrically isolate the second cell 140 from other cells on the substrate 110.

In the present embodiment, the bit line ring BLR2 is located on the source region 146 of the second cell 140. The bit line ring BLR1 is electrically connected to the source region 126. The word line WL5 is electrically connected to the gate region 144 to control the transistor formed by the drain region 142, the gate region 144, and the source region 146. Word line WL6 is electrically connected to gate region 148 to control the transistor formed by drain region 150, gate region 148 and source region 146. Drain terminals 143 and 151 are connected to drain regions 142 and 150, respectively.

FIG. 4 is a cross-sectional view of a third cell 160 in the test array structure 100 of FIG. 1A. The third cell 160 includes a drain region 162, a gate region 164, a source region 166, a gate region 168, and a drain region 170. Each of the gate regions 164 and 168 is formed by a semiconductor region and an insulating region surrounding the semiconductor region. In the cross section provided in fig. 4, the (first) drain region 162, the (first) gate region 164, the (second) source region 166, the (second) gate region 168, and the drain region 170 may be considered to be sequentially arranged and connected together from left to right. Channel region 172 is located below gate regions 164 and 168. Isolation regions IA are formed on both sides of the third cell 160 to electrically isolate the third cell 160 from other cells on the substrate 110.

As shown in fig. 4, the bit line ring BLR2 is electrically connected to the source region 166. Word line WL4 is electrically connected to gate region 164 to control the transistor formed by drain region 162, gate region 164 and source region 166. Word line WL5 is electrically connected to gate region 168 to control the transistor formed by drain region 170, gate region 168, and source region 166. Drain terminal 163 and drain terminal 171 are connected to drain region 162 and drain region 170, respectively.

Refer to fig. 1B and 5 simultaneously. FIG. 5 is a cross-sectional view taken along line C1-C1' of FIG. 1B to illustrate the structure between the first cell 120 and the second cell 140. In other words, fig. 5 also illustrates the structure between two nearest word lines WL4 and WL 5. As shown in FIG. 5, the drain region 130 of the first cell 120 and the drain region 142 of the second cell 140 are located between two nearest word lines WL4 and WL 5. A portion of the bit line ring BLR2 is located between the drain terminal 131 and the drain terminal 143. Drain terminals 131 and 143 are connected to drain regions 130 and 142, respectively.

Isolation region IA is located between drain region 130 and source region 146, and isolation region IA is located below bitline ring BLR2, and another isolation region IA is located between source region 146 and drain region 142. The isolation region IA is used to electrically isolate the first cell 120 and the second cell 140. In some embodiments, the isolation region IA may be a Shallow Trench Isolation (STI).

In this embodiment, two isolation regions IA further surround the drain region 130 and the drain region 142. Specifically, the isolation region IA is disposed around the cells (e.g., the first cell 120, the second cell 140, and the third cell 160) such that the cells are electrically isolated from each other.

Generally, no current can flow between the first cell 120 and the second cell 140 due to the isolation region IA. If the electrical isolation function of the isolation region IA fails due to unexpected reasons, the test array structure 100 can easily measure the current leakage between the first cell 120 and the second cell 140. In other words, referring to fig. 1B and 5 simultaneously, the current leakage in the y-axis direction can be measured. Thus, the test array structure 100 may be formed on a semiconductor substrate or wafer for TEG testing to verify the quality of the semiconductor substrate or wafer. See the subsequent discussion for details.

Please refer to fig. 1C and fig. 6. FIG. 6 is a cross-sectional view taken along line C2-C2' of FIG. 1C, illustrating the drain region 162 of the third cell 160 and the drain region 130 of the first cell 120. Drain terminals 163 and 131 are connected to drain regions 162 and 130, respectively. The isolation region IA is located between the drain region 162 and the drain region 130, or surrounds the drain region 162 and the drain region 130. Therefore, the drain region 162 and the drain region 130 are electrically isolated by the isolation region IA, i.e., the third cell 160 is electrically isolated from the first cell 120.

In fig. 6, word line WL4 is connected to isolation region IA between drain region 162 and drain region 130. Generally, word line WL4 is connected to the gate region of one or more of the cells to control the corresponding transistors within the cell. In this case, although there is no gate region between the drain region 162 and the drain region 130, the word line WL4 is still formed and disposed on the region between the drain region 162 and the drain region 130 for the convenience of the manufacturing process.

In particular, the test array structure 100 may be formed based on a DRAM memory array. In such a case, each bitline ring (e.g., bitline ring BLR1, BLR2, or BLR3) can be considered to consist of two nearest-neighbor bitlines. Two ends of two nearest adjacent bit lines are connected together to form a bit line ring. Therefore, the two nearest adjacent bit lines forming the bit line loop can have the same voltage.

In some embodiments, two adjacent bit lines may have terminals connected to each other, respectively, to apply the same voltage. However, from the viewpoint of modern semiconductor processing, it is difficult to provide two additional terminals on two already formed bit lines, because the size of the device is considered. The dimensions of the semiconductor component are relatively small. In this embodiment, each bitline ring (e.g., bitline rings BLR1-BLR3) is an integrally formed conductive ring, and these integrally formed bitline rings are completed in the same process. In other words, each of the bitline rings is, for example, an oval closed ring formed on the substrate 110 and formed of a conductive material in one process. In such a case, it is not necessary for the bit line loop to be formed by providing an additional terminal or contact to the adjacent bit line. In some embodiments, the test array structure 100 can be fabricated based on native DRAM memory processes.

In addition, generally, no current flows between the adjacent first cell 120 and the third cell 160 due to the isolation region IA. In such a case, if the electrical isolation function of the isolation region IA fails due to an unexpected reason, the test array structure 100 can easily measure the current leakage between the first cell 120 and the third cell 160. In other words, referring to fig. 1C and 6 together, the current leakage along the x-axis direction can also be measured. See the following discussion for specific details.

Therefore, the test array structure 100 may be used to detect current leakage from cell to cell (cell-to-cell) in two directions, and the test array structure 100 may be formed on a semiconductor substrate or wafer for overall quality testing, such as a TEG test.

Fig. 7 shows a schematic top view of a wafer structure 200 according to an embodiment of the invention. The wafer structure 200 has a plurality of dies, and at least one of the dies has a wafer test array as described above. For illustrative purposes, only wafer 210 is shown on the wafer structure in FIG. 7. Therefore, the test array structure 100 can be used for a TEG test to obtain the quality of the wafer structure 200, so as to determine whether the wafer structure 200 is a broken wafer.

FIG. 8 is a flow chart illustrating a wafer testing method 300 according to one embodiment of the present invention. The wafer test method 300 is performed by measuring a test die (e.g., die 210 of fig. 7) on a wafer structure (e.g., the wafer structure 200 of fig. 7) to determine whether the wafer structure 200 is a broken wafer. In the present invention, the test array structure 100 as described above is formed on the test chip 210 to provide a TEG test on a wafer structure. The wafer test method 300 for TEG testing includes flows 310 through 360.

In process 310, a wafer structure 200 having the test array structure 100 as described above is provided, as illustrated in FIG. 7.

As described above, the test array structure 100 has a substrate (e.g., the substrate 110), a plurality of cells (e.g., the first cell 120, the second cell 140, and the third cell 160), a plurality of bit line rings (e.g., the bit line rings BLR1-BLR3), and a plurality of word lines (e.g., the word lines WL1-WL 7). Referring to fig. 2 through 4, the bit line ring BLR2 is connected to the source region 146 of the second cell 140 and the source region 166 of the third cell 160. Word line WL3 is connected to gate region 124 of first cell 120. Word line WL4 is connected to gate region 128 of first cell 120 and to gate region 164 of third cell 160. Word line WL5 is connected to gate region 144 of second cell 140 and to gate region 168 of third cell 160. Word line WL7 is connected to gate region 148 of second cell 140.

In this case, each cell includes two p-type MOSFETs. In the wafer test method 300, applying the turn-on voltage to the source region means providing a driving voltage to the source region, whereas applying the turn-off voltage to the source region means leaving the source region at a floating potential without applying any voltage. In addition, in the present embodiment, applying a turn-on voltage to the gate region means applying a voltage higher than a threshold voltage (threshold) of the p-type MOSFET to the gate region, thereby turning on the transistor in the cell. Conversely, applying a turn-off voltage to the gate region means that no voltage is applied to the gate region and the transistor remains turned off.

Continuing with process 310, in process 320, an on voltage is applied to the (first) bitline ring BLR1 and an off voltage is applied to the (second) bitline ring BLR 2. In this embodiment, the bit line ring BLR2 is floating, but not connected to the driving voltage, while the bit line ring BLR1 is driven by the driving voltage.

Further, at flow 330, turn-on voltages are applied to the first, second, third, and fourth word lines. For the test array structure 100, the first, second, third and fourth word lines correspond to word line WL 3-word line WL4, word line WL5 and word line WL6, respectively, so that in the present embodiment, turn-on voltages are applied to word lines WL3-WL 6. The word lines WL3-WL6 connect different gate regions of the first cell 120, the second cell 140 and the third cell 160, respectively, and thus apply turn-on voltages to the word lines WL3-WL6, i.e., apply voltages higher than the threshold voltage of the p-type MOSFET to the word lines WL3-WL 6. Subsequently, a current between the drain region 130 of the first cell 120 and the drain region 142 of the second cell 140 is measured as a first leakage magnitude. In flow 330, the test array structure 100 is defined to be in state type-A.

Continuing with the process 330, in a process 340, a turn-off voltage is applied to the first and third word lines (corresponding to word line WL3 and word line WL5), and a turn-on voltage is applied to the second and fourth word lines (corresponding to word line WL4 and word line WL 6). For the test array structure 100, the first, second, third and fourth word lines correspond to the word lines WL3-WL6, respectively, i.e., a turn-off voltage is applied to the word line WL3 and WL5, while a turn-on voltage is applied to the word line WL4 and WL 6. The current between the drain region 130 of the first cell 120 and the drain region 142 of the second cell 140 is then measured as a second leakage magnitude. Under flow 340, the test array structure 100 is defined to be in state type-B.

The voltage dependence of the various elements of the test array structure 100 for state type-A of flow 330 and state type-B of flow 340 is shown in FIG. 9. FIG. 9 is a graph illustrating voltage relationships for different regions of the test array structure 100 during different flows of the wafer test method 300.

For the first cell 120, please refer to fig. 2 and 9. Whether for state type-A or state type-B, the bit line ring BLR1 always has a turn-on voltage, and the word line WL4 also always has a turn-on voltage. Thus, for the first cell 120, the source region 126 will always have a turn-on voltage, and the p-type transistor formed by the source region 126, the gate region 128, and the drain region 130 will always be on, which corresponds to the drain region 130 of the first cell 120 always having a relatively high voltage.

For the second cell 140, please refer to fig. 3 and fig. 9. Whether for state type-A or state type-B, the source region 146 of the second cell 140 is always at the turn-off voltage, which causes the source region 146 of the second cell 140 to always have a floating potential.

However, in the test array configuration at state type-a of flow 330, the word line WL5 has a turn-on voltage, which turns on the transistor consisting of the source region 146, the gate region 144, and the drain region 142, and also causes the drain region 142 of the second cell 140 to have a relatively low voltage. In the process 330, since the drain region 130 of the second cell 140 always has a high voltage and the drain region 142 of the second cell 140 always has a low voltage, if the isolation region IA between the drain region 130 and the drain region 142 has a short circuit caused by an unexpected defect, there will be a leakage current between the drain region 130 and the drain region 142. The measured leakage current between drain region 130 and drain region 142 is the first leakage magnitude.

In flow 340, the test array structure is in state type-B of flow 330, the word line WL5 has an OFF voltage, which causes the transistor comprised of the source region 146, gate region 144, and drain region 142 to be OFF. This corresponds to that no current flows in the transistor formed by the source region 146, the gate region 144 and the drain region 142. Therefore, in the test array structure in the state type-B of the process 330, there is theoretically no leakage current between the drain region 130 and the drain region 142 even if the isolation region IA between the drain region 130 and the drain region 142 has a short circuit caused by an unexpected defect. The leakage current between drain region 130 and drain region 142 may then be measured as a second leakage magnitude. In general, the second leakage magnitude will be a value that approaches zero.

Continuing with the process 330 and the process 340, in the process 350, it is determined whether a current leakage occurs between the first cell 120 and the second cell 140 by comparing the first leakage magnitude and the second leakage magnitude. As previously discussed, if the isolation region IA between drain region 130 and drain region 142 has an unexpected defect that results in a short circuit, the first leakage magnitude of state type-a in flow 330 will be quite different from the second leakage magnitude of state type-B in flow 340.

FIG. 10 is a graph depicting the magnitude of leakage at various locations in the test array structure 100. The horizontal axis is the coordinate label of different locations on the test array structure 100 corresponding to different current flow paths. The vertical axis is the leakage amplitude of the current flow path. Each coordinate mark corresponds to the current flowing through the corresponding current flowing path between two adjacent drain regions.

FIG. 10 shows the magnitude of leakage at different locations on the test array structure 100 for both states type-A and type-B, and is used to compare the magnitude of leakage. As indicated in fig. 10, the first leakage amplitude and the second leakage amplitude are indicated at positions corresponding to positions between two adjacent drain regions 130 and 142 of the first cell 120 and the second cell 140. That is, under the measurement results of fig. 10, it can be confirmed that there is current leakage between the first cell 120 and the second cell 140. This current leakage occurs between the first cell 120 and the second cell 140 along the x-axis direction.

By comparing the results shown in fig. 10, if there is a current leakage between the first cell 120 and the second cell 140, it can be confirmed that the wafer structure 200 is a broken wafer. In process 360, if there is current leakage between the first cell 120 and the second cell 140, the wafer structure 200 may be marked as a broken wafer, and the broken wafer structure 200 may be subsequently removed.

FIG. 11 is a flowchart illustrating a continuation of the wafer test method 300 of FIG. 8. In the present embodiment, the current leakage in the x-axis direction can be measured through the flow 370 to the flow 390.

In flow 370, a third leakage magnitude is measured, where the third leakage magnitude is a current between the drain region 130 of the first cell 120 and the drain region 162 of the third cell 160.

Refer to the table of fig. 9 and fig. 4. Regardless of the state type-A or the state type-B, the bit line ring BLR2 always has an OFF voltage, and the word line WL4 always has an ON voltage. Source region 166 has an off voltage and is at a floating voltage. Gate region 164 has an on voltage. Thus, the transistor formed by the source region 166, gate region 164, and drain region 162 is always on, and the drain region 162 always has a low voltage. If the isolation region IA between drain regions 130 and 162 has a short circuit caused by an unexpected defect, a current will be measured between drain regions 130 and 162. The current flow between drain region 130 and drain region 162 is as a third leakage magnitude.

In the process 380, it is determined whether a current leakage occurs between the first cell 120 and the third cell 160 according to the magnitude of the third leakage amplitude. As shown in fig. 6, if the isolation region IA between the drain region 130 and the drain region 162 has an unexpected defect to cause a short circuit, the third leakage amplitude between the first cell 120 and the third cell 160 may be larger than a predetermined standard value. Thus, whether or not there is a current leakage between the first cell 120 and the third cell 160 can be confirmed. If the current leakage occurs, the current leakage between the first cell 120 and the third cell 160 occurs in the x-axis direction.

In the process 390, if a current leakage occurs between the first cell 120 and the third cell 160, the wafer structure 200 is marked as a damaged wafer. After the wafer test method 300 is completed, the marked broken wafer structure 200 may be removed.

In summary, the present invention provides a test array structure capable of being used for wafer testing. The test array structure can be fabricated according to existing DRAM processes based on existing DRAM memory arrays. The test array structure can be used to measure current leakage in two directions perpendicular to each other. The test array structure can be arranged on the wafer structure to be tested, so that the quality of the wafer structure can be confirmed and checked.

Although the present invention has been described with reference to the above embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention.