TW201320212A - Testkey structure and method for measuring step height by such testkey structure - Google Patents

Abstract

A testkey structure for use in measuring step height includes a substrate, and a pair of test contacts. The substrate includes an isolation region and a diffusion region. The test contact pair includes a first test contact and a second test contact for measuring electrical resistances. The first test contact is disposed on the diffusion region and the second test contact is disposed on the isolation region.

Description

Test key structure and method of using this test key structure to measure stage height

The present invention generally relates to a test key structure and a method of using the test key structure to measure a step-height. In particular, the present invention relates to a test key structure for measuring electrical resistance and a method of using the test key structure to measure the height of a stage.

Smooth and flat silicon wafers are the basis for making integrated circuits. The difference in the level of formation of each component in the wafer, such as the height difference between the shallow trench isolation (STI) of the metal oxide semiconductive crystal (MOSFET) and the active region of the adjacent transistor. It will cause unevenness on the surface of the substrate, which is called the stage height. These stages are highly critical to the success of semiconductor processes.

These key impacts can cover multiple aspects. For example, in the process, the degree of unevenness of the surface of the substrate has a major influence on the accuracy of the lithographic exposure, such as problems such as defocus or distortion. In terms of component characteristics, it will affect the reliability of the component. For example, the junction surface of the substrate and the junction leakage characteristics of the device isolation characteristics and other characteristics of the device include a short channel effect (SCE) and a narrow width effect (NWE). Has a high degree of correlation. Therefore, if there is a need for stable process control, such as chemical mechanical polishing or a yellow light process, a method is needed to know the stage height of the substrate, both quickly and without destroying the substrate.

There are currently known methods for knowing the stage height of the substrate. For example, an atomic force microscope (AFM) can be used to see the surface condition of a substrate, but it is not possible to observe a sufficient range of surfaces in a limited time.

Another known method can also be used to know the stage height of the substrate, which is called Transmission Electron Microscopy (TEM). Although the use of a penetrating electron microscope is less time-consuming than atomic force microscopy, it is necessary to obtain a substrate sample in a destructive manner. In view of the current technology, there is no way to know that the height of the substrate stage is the best of both worlds, so there is still room for improvement in the current method of knowing the height of the substrate stage.

The present invention thus proposes a test key structure and a method of using the test key structure to measure the stage height. The invention is characterized by at least a fast, accurate and non-destructive acquisition stage height.

The present invention first proposes a test key structure. The test key structure of the present invention comprises a substrate and a set of test contacts. The substrate has an insulating region and a diffusion region, and a set of test contacts includes a first test contact for measuring resistance and a second test contact. The first test contact is in the diffusion region and the second test contact is in the insulating region. By thus testing the bond structure, the stage height of the substrate surface can be indirectly known.

The present invention then proposes a method of using this test key structure to measure the height of the surface phase of the substrate. First, a test key structure is provided. The test key structure includes a first test contact and a second test contact, and the first test contact and the second test contact have a one-stage height. Secondly, the first test resistance value and the second test resistance value are respectively measured through the first test contact and the second test contact. Then, referring to a database, the first test height corresponding to the first test resistance value and the second test height corresponding to the second test resistance value are independently obtained. Next, the first test height and the second test height are calculated, ie the stage height can be obtained in a non-destructive manner.

In an embodiment of the invention, the method for measuring the height of the stage may further comprise the following steps. First, multiple sets of test contacts of different heights are provided. Secondly, a larger number of test resistance values were respectively contacted via multiple sets of tests. Then, measure the heights of multiple sets of test contacts. Then, a plurality of sets of test resistance values corresponding to a plurality of sets of heights are integrated, and a database can be established.

Since the present invention can independently contact the second test contact via the first test contact in the test key structure, the corresponding first test height and the corresponding second test height are independently obtained. In addition, by calculating the first test height and the second test height, a one-stage height can be obtained in a non-destructive manner. Therefore, the present invention can know the stage height of the substrate in a fast and non-destructive manner. The method of the present invention for measuring the height of the substrate stage has the best of both worlds, so that the stable control of the process can be carried out smoothly without breaking the substrate.

The present invention provides a test key structure for non-destructive measurement of the stage height of a surface of a substrate, such as a shallow trench separating the surface height caused by the surface of the substrate.

Please refer to FIGS. 1 to 3, and FIGS. 1 to 3 illustrate a method of forming the test key structure of the present invention. First, as shown in FIG. 1, a plurality of trenches 103 for forming shallow trench isolation are etched into the substrate 101 using the hard mask 102. The substrate 101 may include a wafer region 104 and a test keypad 105, and the wafer region 104 and the test keypad 105 may respectively include an insulating region 106 and a diffusion region 107. In addition, the hard mask 102 may be a single film layer or a stacked film layer containing a material such as a nitrogen cerium compound or a cerium oxide compound.

Subsequently, as shown in FIG. 2, the insulating material is filled into the trench 103, and after the planarization forms the shallow trench isolation 110, the hard mask 102 is removed. Due to the thickness of the hard mask 102, the shallow trench isolations 110 in the insulating regions 106 will protrude from the surface of the substrate 101 of the wafer region 104 and the test keypad 105, respectively, with a one-stage height. In addition, in other embodiments, the shallow trench isolation 110 in the insulating region 106 can also be replaced with other insulating materials, such as directly forming an oxide layer on the surface of the substrate 101 by oxidation to form a field oxide layer (not shown).

Next, as shown in FIG. 3, a desired semiconductor process is performed, for example, an ion well (not shown), a gate structure, a source doping region (not shown), and a gate doping are formed on the substrate 101. A region (not shown) or the like is used to cover the gate structure with an insulating material to form an interlayer insulating layer 108, and then a planarization process such as chemical mechanical polishing is used to remove excess insulating material until the gate structure is exposed. At this time, the gate structure 115 in the wafer region 104 is the gate of the metal oxide semiconductor (MOS) device, and the gate structure 117 on the shallow trench isolation 110 may be the passing gate. Components such as resistors or electrical fuses (eFuse).

It is noted that the germanium gate structure simultaneously formed in the test keypad 105 along with the semiconductor processes becomes a set of test contacts 120 of the present invention. This set of test contacts 120 includes a first test contact 121 and a second test contact 125. The locations of the first test contact 121 and the second test contact 125 in the test keypad 105 are not the same, for example, on the diffusion region 107 and the insulating region 106, respectively. Since the surface of the shallow trench isolation 110 protrudes from the surface of the substrate 101 to have a stage height and is subjected to chemical mechanical polishing, the top surface of the first test contact 121 of the present invention shares a plane with the top surface of the second test contact 125. Therefore, in the embodiment, the thickness of the first test contact 121 and the second test contact 125 are different. As shown in FIG. 3, the thickness of the first test contact 121 on the surface of the substrate 101 is greater than that of the shallow trench isolation 110. The thickness of the second test contact 125 of the surface, and the difference in thickness between the two is the height of this stage.

Optionally, the wafer region 104 or at least one gate structure of the test keypad 105 may be selectively converted into a metal gate structure by a gate-last process such as a gate-gate and a gate gate. A necessary source contact plug (not shown) or a drain contact plug (not shown) and a contact plug electrically connected to the first test contact 121 and the second test contact 125, respectively, are formed around the structure ( The figure is not shown). For example, one or both of the first test contact 121 and the second test contact 125 can be converted to a metal gate structure. The method of converting to a metal gate structure may be to first form a desired gate trench through an etching step in the gate structure, and then to apply a suitable metal such as a work function metal layer, a barrier layer, aluminum, copper, etc. The metal is filled in the gate trench while covering the interlayer insulating layer 108, and the excess metal is removed by chemical mechanical polishing until the interlayer insulating layer 108 is exposed, thereby forming a metal gate structure. Through the above steps, the first test contact 121 and/or the second test contact 125 can be independently a metal gate structure or a germanium gate structure.

Through the foregoing steps, the germanium gate structure and/or the metal gate structure in the wafer region 104 can be obtained, and also located in the test keypad 105 corresponding to the gate gate structure and the metal gate structure in the wafer region 104. The test key structure 120 of the present invention. Because the thickness difference between each gate structure in the test keypad 105 and the wafer region 104 and each test contact is the stage height of the shallow trench isolation 110, the test key structure 100 of the present invention can be correspondingly simulated and measured. The stage height in the wafer area 104. The test key structure 100 of the present invention comprises a substrate 101 and a set of test contacts 120. Substrate 101 has a wafer area 104 and a test keypad 105 adjacent wafer area 104. Both the wafer region 104 and the test keypad 105 include an insulating region 106 and a diffusion region 107, respectively. The insulating region 106 may be a shallow trench isolation 110 or a field oxide layer (Fox) embedded in the substrate 101.

As still shown in FIG. 3, the set of test contacts 120 of the preferred embodiment includes two first test contacts 121 and second test contacts 125 for measuring resistance. For example, the first test contact 121 is located above the diffusion region 107 of the ion well, the source doped region and the drain doped region, but does not contact the insulating region 106. That is, the first test contact 121 is surrounded by a diffusion region, and the second test contact 125 is located above the insulating region 106 but does not contact the diffusion region 107, and the first test contact 121 is in contact with the second test. One of the 125 is surrounded by the other, and between the first test contact 121 and the second test contact 125 there is an interlayer insulating layer 108. The test bond structure 100 of the present invention can be used to perform a wafer acceptance test (WAT), and via the test bond structure 100, the stage height of the substrate surface can be indirectly known.

If the first test contact 121 has a height H ₁ and the second test contact 125 has a height H ₂ , the drop ΔH between the first test contact 121 and the second test contact 125 is the stage height (ΔH=H ₁ -H ₂ ) .

In addition, the first test contact 121 and the second test contact 125 in the test key structure 100 of the present invention can have a variety of different layout modes. Please refer to FIG. 4, which shows a top view of an embodiment of the test key structure of the present invention. The test key structure 100 of the present invention includes a set of test contacts 120. The set of test contacts 120 includes a first test contact 121 and a second test contact 125 for measuring resistance. The first test contact 121 is in a strip and the first test contact 121 is surrounded by the diffusion region 107. Furthermore, the second test contact 125 is located around the first test contact 121 and simultaneously encloses the first test contact 121 and the diffusion region 107 in a straight strip shape. The first test contact 121 and the second test contact 125 respectively have conductive plugs 131/135 for electrical connection.

It should be noted that FIG. 4 is merely an illustration, and the positions of the conductive plugs 131/135 are not limited to the ends of the first test contact 121 and the second test contact 125. There is also no limitation on the relative length of the first test contact 121 and the second test contact 125.

Since the gate conductor in the gate will have a resistive property, such as sheet resistance, and the sheet resistance and the thickness of the conductor material, that is, the height of the gate conductor, are highly correlated with each other. Therefore, in theory, under the same channel length, the higher the height of the gate conductor, the larger the cross-sectional area, and the smaller the sheet resistance value, so the present invention measures the test key structure. The sheet resistance can be used in a non-destructive manner to know the height of the gate conductor and the stage height of the substrate surface. For example, the sheet resistance of the first test contact 121 is measured by the conductive plug 131 to be ρ ₁ , so that the height H ₁ can be derived. Similarly, the sheet resistance of the second test contact 125 is measured by the conductive plug 135 to be ρ ₂ , so that the height H ₂ can be derived. In the present embodiment, the height H _{1 is} greater than the height H ₂ , so the difference between the height H ₁ and the height H ₂ is the stage height ΔH.

The present invention then provides a method of using a test key structure to measure the height of a surface stage of a substrate. Figures 5 through 6 illustrate an embodiment of the method of the present invention for measuring the surface height of a substrate using a test key structure. First, please refer to FIG. 3 to provide a test key structure 100. The description of the test key structure 100 of the present invention can be referred to the foregoing. Next, referring to FIG. 5, the first test resistance value ρ ₁ and the second test resistance value ρ2 are respectively measured through the first test contact 121 and the second test contact 125. The two test resistance values ρ1 and ρ2 can be measured by a 2-point probe, but it is not limited to this measurement method, for example, 4-point probe measurement is also possible. Then, referring to FIG. 6, refer to a database, which provides a test with a test resistance value ρ off between the height H of the connected, test and obtain a first resistance value corresponding to the first test ρ height H ₁ of _1, corresponding to the second The second test height H _{2 of the} resistance value ρ ₂ is tested. Next, the first test height H ₁ and the second test height H _{2 are} independently calculated, ie the stage height ΔH can be obtained in a non-destructive manner.

The database used to refer to the test height can be obtained, for example, by the following method. For example, a plurality of sets of conductors of gate structures and the like having different heights may be provided first. The height of the actual gate structure can also be measured using a variety of conventional methods, such as atomic force microscopy or transmissive electron microscopy. At the same time, the test resistance values of the individual gate structures are separately measured through the test contacts. After providing a sufficient number of sets of samples, a database of resistance values corresponding to the height of the gate structure as shown in Fig. 5 can be obtained. Alternatively, the database may be further organized to obtain a formula H of the resistance value ρ corresponding to the height of the gate structure. E.g:

H=aρ+k

Where a coefficient, k is a correction constant. In addition, the conductors in the test contact may also contain different conductive materials. For example, aluminum or enamel. If the materials touched by the test are different, you can refer to the previously exemplified method to provide multiple sets of samples with different materials and heights, and you can collect the data with different resistance levels as shown in Figure 5.

In addition, the test bond structure formed by different conductive materials can also be measured separately. For example, the test bond structure formed by bismuth, and the test bond structure formed of aluminum. In theory, although the stage height ΔH is independent of the material of the test key structure, the actual measurement results may be different. However, the phase height ΔH obtained from different conductive materials, respectively, can be used to estimate the error range of the phase height ΔH.

The stage height obtained by the above method, for example, 50 nanometers (nm) to 60 nm, can be used to verify the reliability and quality of the semiconductor structure. If the resulting phase height does not meet the expected value, such as exceeding the expected value or less than the expected value, a subsequent component modification step can be initiated, or the semiconductor process of the previous stage can be fed back and adjusted to ensure the semiconductor structure. Reliability and quality.

In summary, the present invention provides a method for measuring the height of a surface stage of a substrate using a test key structure and a test key structure thereof. One of the features is that two or more test contacts are formed, which can be designed and placed. Next to the product components, indirectly, instantaneously and non-destructively confirm whether the stage height of the product components is as expected.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100. . . Test key structure

101. . . Substrate

102. . . Hard mask

103. . . ditch

104. . . Wafer area

105. . . Test keypad

106. . . Insulating area

107. . . Diffusion zone

108. . . Interlayer insulation

110. . . Shallow trench isolation

115. . .矽 gate structure

117. . .矽 gate structure

120. . . a set of test contacts

121. . . First test contact

125. . . Second test contact

131/135. . . Conductive plug

Figures 1 through 3 illustrate a method of forming the test bond structure of the present invention.

Figure 4 is a top plan view of an embodiment of the test key structure of the present invention.

Figures 5 through 6 illustrate an embodiment of the method of the present invention for measuring the surface height of a substrate using a test key structure.

100. . . Test key structure

101. . . Substrate

104. . . Wafer area

105. . . Test keypad

106. . . Insulating area

107. . . Diffusion zone

108. . . Interlayer insulation

110. . . Shallow trench isolation

115. . .矽 gate structure

117. . .矽 gate structure

120. . . a set of test contacts

121. . . First test contact

125. . . Second test contact

Claims (20)

A test key structure includes: a substrate having an insulating region and a diffusion region; and a set of test contacts including a first test contact and a second test contact for measuring A resistor, wherein the first test contact is located in the diffusion region and the second test contact is located in the insulation region. The test key structure of claim 1, wherein the first test contact comprises a first gate structure that does not contact the insulating region and is one of a metal gate and a gate, the second test contact includes Contacting the diffusion region is a second gate structure of one of a metal gate and a gate. The test key structure of claim 1, wherein the insulating region and the diffusion region have a step height. The test key structure of claim 1, wherein a top surface of the first test contact shares a plane with a top surface of the second test contact. The test key structure of claim 1, wherein the thickness of the first test contact is greater than the thickness of the second test contact. The test key structure of claim 1, wherein the first test contact is surrounded by the diffusion region. The test key structure of claim 1, wherein the first test contact and the second test contact one of the other. The test key structure of claim 1, wherein both ends of the first test contact and the second test contact are electrically connected to a contact plug. A method for measuring a step height, comprising: providing a test key structure including a first test contact and a second test contact, and the first test contact and the second test contact have a stage height Receiving a first test resistance value and a second test resistance value respectively through the first test contact and the second test contact; and referring to a database, obtaining a first test height corresponding to one of the first test resistance values And a second test height corresponding to one of the second test resistance values; and calculating a difference between the first test height and the second test height to obtain the stage height in a non-destructive manner. The method of claim 9, wherein the test key structure further comprises: a substrate comprising an insulating region and a diffusion region, wherein the first test contact is located above the diffusion region but not The insulating region is contacted while the second test contact is above the insulating region but does not contact the diffusion region. A method of measuring the height of a stage as claimed in claim 9, wherein the insulating region protrudes from the surface of the substrate and forms a height with the diffusion region. A method of measuring a stage height according to claim 9, wherein a top surface of the first test contact shares a plane with a top surface of the second test contact. A method of measuring a stage height as claimed in claim 9, wherein the thickness of the first test contact is greater than the thickness of the second test contact. The method of claim 9, wherein the at least one of the first test contact and the second test contact is a metal gate. The method of claim 9, wherein the first gate structure and the second gate structure are at least one gate. A method of measuring a stage height as in claim 9, wherein the first test contact is surrounded by the diffusion zone. A method of measuring a stage height as claimed in claim 9, wherein the first test contact is in contact with the second test to surround the other. The method of measuring the height of the stage of claim 9, further comprising providing a plurality of sets of test contacts having different heights; respectively, measuring a plurality of sets of test resistance values by the plurality of sets of test contacts; measuring the plurality of sets of test contact heights; (integrate) A set of test resistance values corresponding to multiple sets of heights to establish the database. A method of measuring the height of a stage, as in claim 18, wherein a destructive manner is used to measure the plurality of sets of heights of the plurality of sets of test contacts. A method of measuring the height of a stage, as in claim 9, wherein a component correction step is performed when the height of the stage is not as expected.