High-power device fault localization via die surface profiling

Abstract

A method of preparing a computer processor die includes determining a warpage shape of the computer processor die at a test temperature. The method also includes selectively contouring the thickness of the computer processor die at a contouring temperature by physically removing material from a surface of the computer processor die so that the surface is substantially planar at the test temperature.

Description

Technical Field

[0001] The present invention relates to computer processors and, more particularly, to the fabrication of devices for testing processor designs. Background Art

[0002] Traditional methods for testing and analyzing electronic devices (such as microprocessors) can involve image-based fault localization tools such as laser scanning microscopes (LSM) or photon emission microscopes (PEM). Using LSM and PEM can involve operating the device under test (DUT) at maximum frequency and power, so the DUT should be continuously cooled during testing. If cooling is insufficient, thermal runaway can occur, in which the DUT temperature increases until the DUT fails.

[0003] In addition to cooling, there should be an optically clear path between the DUT and the microscope lens during testing so that the DUT can be observed. Unfortunately, this path prevents the use of common methods for heat removal, such as thermal interface materials and heat sinks. In addition, for ultra-high-resolution imaging using LSM and PEM, a solid immersion lens (SIL) is often used to make direct surface contact with the back of the DUT, further complicating the task of cooling the DUT. Summary of the Invention

[0004] According to an embodiment of the present disclosure, a method of manufacturing a computer processor die includes determining a warped shape of the computer processor die at a test temperature. The method also includes selectively contouring the thickness of the computer processor die at a contouring temperature by physically removing material from a surface of the computer processor die so that the surface is substantially flat at the test temperature.

[0005] According to an embodiment of the present disclosure, a method for preparing a computer processor die for testing includes heating the computer processor die to an initial temperature, attaching a forming material to the computer processor die to maintain the shape of the computer processor die near the initial temperature, selectively contouring the thickness of the computer processor die by physically removing material from a surface of the computer processor die, and separating the computer processor die from the forming material.

[0006] According to an embodiment of the present invention, a system includes a computer processor die, a laminate material coupled to the computer processor die, a daughter card electrically coupled to the computer processor die to power the computer processor die, a solid immersion lens in contact with a backside of the computer processor die, and a cooling plate in contact with the backside of the computer processor die. The backside of the computer processor die is substantially flat at an operating temperature of the computer processor die. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 FIG. 4 is a side view of a processor testing device according to an embodiment of the present disclosure.

[0008] Figures 2A-2D is a pair of side views (on the left) and topography images (on the right) of the device under test (DUT) at different temperatures.

[0009] Figure 3 is a side view of a profiled replacement die at room temperature according to an embodiment of the present disclosure.

[0010] Figure 4 is a flow chart of a method of contouring a die according to an embodiment of the present invention.

[0011] Figures 5A-5D is a pair of side views (on the left) and topography images (on the right) of a profiled device under test (DUT) at different temperatures according to an embodiment of the present disclosure.

[0012] Figures 6A-6D is a series of side views of an alternative die contoured on a mount according to an embodiment of the present disclosure.

[0013] Figure 7 is a flow chart of an alternative method of contouring a die according to an embodiment of the present invention. DETAILED DESCRIPTION

[0014] Figure 1 1 is a side view of test apparatus 100. In the illustrated embodiment, test apparatus 100 includes die 102, laminate 104, POGO interposer 106, and daughter card 108. In the depicted case, die 102 is a microprocessor of a DUT, and thus die 102 is electrically and structurally connected to laminate 104 via solder joints 110. Laminate 104 is electrically connected to POGO interposer 106 via POGO pins 112, and laminate 104 is structurally connected to POGO interposer 106 via a clamping frame 114. POGO interposer 106 is electrically and structurally connected to daughter card 108, so that electrical components of die 102 (not shown, but positioned on a side of die 102 proximate to laminate 104) can be selectively powered through daughter card 108.

[0015] Furthermore, the test apparatus 100 includes a SIL 116 that can be moved along a surface of the die 102 proximate to the laminate 104 (i.e., the "back" or "top" of the die 102, although such directional indicators are used only to reference the orientation of the components shown in the figures). Furthermore, the test apparatus 100 includes a cooling plate 118 that surrounds the SIL 116 and moves therewith across the surface of the die 102. Thus, the die 102 can be handled, tested, observed, and cooled within the test apparatus 100.

[0016] Figures 2A-2D 1 is a pair of side views (on the left) and topography (on the right) of die 102 (DUT) at different temperatures of 25°C, 85°C, 160°C, and 220°C, respectively. These views are significantly exaggerated so that the characteristics described are easier to see. In addition, to facilitate understanding of the topography, different contour lines have been used to indicate different elevations. From lowest to highest, the line pattern is solid, dashed only, dotted double dotted, and dot only.

[0017] In the embodiment shown, die 102 has a constant thickness, and it and laminate 104 have a convex shape that varies, for example, by about 85 μm from corner to center at 25°C (e.g., when die 102 is inactive). At 85°C (e.g., when die 102 is operating normally), die 102 and laminate 104 are less convex and vary, for example, by about 50 μm from corner to center. At 160°C (e.g., when die 102 is overheated), die 102 and laminate 104 are substantially flat. Although die 102 may have small ripples on its back side due to uneven self-heating from internal electrical activity, the basic flatness can be, for example, less than about 10 μm. At 220°C (e.g., when die 102 is extremely overheated), die 102 and laminate 104 have a concave shape and vary, for example, by about 20 μm from corner to center.

[0018] Thus, at 25°C, the die 102 has very limited contact with the cooling plate 118, and at 85°C and 220°C, the die 102 has limited contact with the cooling plate 118, and at 160°C, the die 102 has the most extensive contact with the cooling plate 118. Unfortunately, this temperature may be significantly higher than the normal operating temperature of the die 102, at which testing would be most valuable. Due to the limited cooling available at 85°C, the temperature of the die 102 may rise above 85°C even under normal operating conditions, because the techniques that will be used on the production device will not be available for use on the test device 100 ( Figure 1), the die 102 is cooled in the test apparatus 100. More specifically, known industry methods for cooling the DUT within the test apparatus 100 (e.g., such as methods employing LSM) involve direct contact between the die 102 and the cooling plate 118. However, the die 102 may be very large, with complex surface topography, which may result in a loss of contact cooling (i.e., conduction) with the cooling plate 118. Moreover, self-heating within the die 102 may result in dynamic thermal warping, leading to a loss of critical contact area and subsequent loss of cooling. Additionally, many direct contact cooling plate solutions (e.g., cooling plate 118) are not designed for ultra-high power applications and do not account for the significant non-uniform power dissipation found, for example, in large-scale multi-core server processors.

[0019] Figure 3 is a side view of an optional die 130 formed at approximately room temperature (eg, 25° C.). In the embodiment shown, the die 130 is attached to the laminate 104 and may be in a state of being in contact with the laminate. Figure 2A The die 130 is cut by tool 132, which selectively thins and contours the die 130. This is illustrated by thickness T2 being less than thickness T1, which is the original uniform thickness of the die 130 before contouring. Furthermore, edges E1 and E2 indicate the boundaries where the contouring operation occurs, outside of which the contouring operation remains uncontoured, having thickness T1.

[0020] The laminate 104 and / or tool 132 can be fixed and / or moved (e.g., rotated and / or translated in space) by a computer numerical control (CNC) machine (not shown) to selectively profile the back side of the die 130. The tool 132 can be any suitable localized material removal device. Although the tool 132 is depicted as an end mill, the tool 132 can alternatively be, for example, a ball mill, a drill bit (e.g., carbide or diamond), a sandstone, a grinding stone, or a polishing wheel. In addition, a plurality of different tools 132 can be used sequentially, for example, to selectively remove material and then polish some or all of the back side of the die 130 to a mirror finish. Thus, the die 130 can be subjected to a plurality of different tooling steps in the test apparatus 100 ( Figure 1 ) is formed prior to testing in FIG. 1 such that die 130 is substantially flat at its operating temperature.

[0021] Figure 4 is a flow chart of a method 140 for contouring a die 130. During the discussion of the method 140, reference may be made to Figure 1-3 Features shown in .

[0022] At block 142, the operating temperature of die 130 is determined. The operating temperature can be, for example, the normal operating temperature of a production processor having the same design as die 130. At block 144, a test temperature for die 130 is determined. The test temperature can be, for example, substantially similar to the operating temperature (e.g., plus or minus 10°C) or substantially different from the temperature at which die 130 will be tested (e.g., to simulate startup or overheating conditions). At block 146, a previous virtual model of the uncontouring die 130 is created using finite element analysis. At block 148, the previous warped shape of the uncontouring die 130 is calculated by analyzing the previous virtual model at the test temperature. At block 150, the previous warped shape is selectively thinned to create a subsequent virtual model that will have a substantially flat backside at the test temperature. At block 152, the subsequent warped shape of die 130 is calculated by analyzing the subsequent virtual model at the contouring temperature (e.g., the temperature at which die 130 will be thinned, e.g., approximately room temperature). At block 154 , the difference between the uncontoured die 130 and the subsequent warped shape is calculated to determine the amount of material to remove at different locations on the backside of the die 130 .

[0023] At block 156, the non-contoured die 102 is mounted to the laminate 104. At block 158, the die 102 is contoured at the contouring temperature, for example, by removing material from the backside of the die 102 to create a contoured die 130 so that the die 130 matches the subsequent warping shape. This will result in the die 130 having the same shape as the subsequent dummy model, so that the die 130 will be substantially flat at the test temperature. At block 160, the backside of the die 130 is polished to, for example, a mirror finish. At block 162, the laminate 104 (with the die 130) is then secured in the test fixture 100 by attaching the laminate 104 to the POGO interposer 106. Once secured, the backside of the die 130 is in contact with the cooling plate 118. At block 164 , the die 130 is tested by energizing and operating the die 130 while being observed by the SIL 116 and cooled by the cooling plate 118 .

[0024] Method 140 allows for selective thinning of die 130 by virtually modeling a non-contoured die at a common temperature (e.g., room temperature), virtually heating die 130, virtually modifying die 130 to be substantially flat at the elevated temperature, virtually cooling die 130, and calculating the material that needs to be removed at the common temperature. Additionally, some alternative embodiments include iteratively repeating blocks 146 and 152 one or more times, as indicated by dashed arrows. This can further refine the shape of mold 130 to increase contact and heat transfer between die 130 and cooling plate 118. In each iteration, the subsequent virtual model becomes the previous virtual model for the next iteration.

[0025] Figures 5A-5D 1 is a pair of side views (on the left) and topography (on the right) of a die 130 (DUT) at different temperatures, 25°C, 85°C, 160°C, and 220°C, respectively. These views are significantly exaggerated so that the characteristics described are easier to see. In addition, to facilitate understanding of the topography, different contour lines have been used to indicate different elevations. From lowest to highest, the line pattern is solid, dashed only, dotted, double dotted, and dotted only.

[0026] In the illustrated embodiment, die 130 has a selectively thinned thickness, and it and laminate 104 have a convex shape that varies, for example, by approximately 50 μm from corner to center at 25°C (e.g., when die 130 is inactive). At 85°C (e.g., when die 130 is operating normally), laminate 104 is less convex, and die 130 is substantially flat. Although die 130 may have small ripples on its backside due to uneven self-heating from internal electrical activity, the substantial flatness can be, for example, less than approximately 10 μm. At 160°C (e.g., when die 130 is overheated), laminate 104 is substantially flat, and die 130 has a concave shape that varies, for example, by approximately 40 μm from corner to center. At 220°C (e.g., when die 130 is extremely overheated), die 102 and laminate 104 have a concave shape that varies, for example, by approximately 60 μm from corner to center.

[0027] Die 130 has an operating temperature of 85°C, and thus, die 130 has been selectively thinned to be substantially flat at 85°C; however, if a different operating temperature is desired or predicted, method 140 may be performed again using the new temperature. Thus, die 130 may be substantially flat at the new temperature, which is not possible with known methods, such as a die having a constant thickness (e.g., Figures 2A-2D shown) or simply flattening the die at room temperature (not shown).

[0028] Figures 6A-6D There is a series of side views of die 102 being contoured on mount 172, transforming it into die 170. Mount 172 includes a stud 174 and a former 176, and is connected to laminate 104. Stud 174 is a rigid plate made, for example, of steel or aluminum.

[0029] In the illustrated embodiment, former 176 is a material that is formable at relatively low temperatures but is solid at room temperature. More specifically, former 176 can solidify, dry, and / or cure at a temperature similar to the operating temperature of die 170 (e.g., plus or minus 10° C.), and thus former 176 can be solid at the contouring temperature but retain the shape of die 170 at or near the die's operating temperature. Thus, former 176 can include, for example, a thermosetting polymer material (e.g., a resin) or a thermoplastic polymer material (e.g., a wax).

[0030] To secure the mount 172 to the laminate 104, the laminate 104 and die 170 can be heated (e.g., by operation of the die 170 or by an external source such as an oven) and placed proximate the posts 174. The former 176, in fluid form, can then be poured between the posts 174 and the laminate 104. The former 176 then solidifies, dries, and / or cures and adheres the laminate 104 to the posts 174. In an alternative embodiment, the former 176 is formed into a solid that approximates the shape of the laminate 104 at the operating temperature of the die 170. The former 176 then adheres to the posts 174, and the heated laminate 104 adheres to the former 176. Adherence of the laminate 104 to the former 176 can occur, for example, by pressing the laminate 104 onto the former 176, locally melting the surface of the former 176. For another example, a thin layer of adhesive (eg, glue) (not shown) is added between the former 176 and the laminate 104 to bond them together.

[0031] Reference Figure 6B , die 170 is being cut into a planar form by tool 178. This action selectively thins die 170 and contours it to be substantially flat at the operating temperature of die 170. This operation can be performed at approximately room temperature because die 170 is physically constrained in its shape at operating temperature. In the illustrated embodiment, post 174 and / or tool 178 can be fixed and / or moved (e.g., rotated and / or translated in space) by a computer numerically controlled (CNC) machine (not shown) to selectively contour the backside of die 170. The tool can be any suitable localized or planar material removal device. While tool 178 is depicted as a grinding tool, tool 132 can alternatively be, for example, an end mill, a fly cutter, a drill bit (e.g., carbide or diamond), a grindstone, or a polishing wheel. Furthermore, multiple different tools 178 can be used sequentially, for example, to selectively remove material and then polish some or all of the backside of die 170 to a mirror finish.

[0032] Reference Figure 6CAfter the die 170 is contoured, for example, by removing the former 176, the mount 172 is removed from the laminate 104. In some embodiments, the former 176 is removed by a chemical (e.g., dissolving), thermal (e.g., heating), and / or mechanical (e.g., cutting) process. After the mount 172 is broken, the laminate 104 and the die 170 assume their natural shape at approximately room temperature, which may be more convex than at the test temperature.

[0033] exist Figure 6D The difference between die 170 before and after contouring is shown in FIG. 1 by thickness T3 being less than thickness T1 (shown in dashed lines). Additionally, edges E3 and E3 indicate the boundaries where the contouring operation occurs, outside of which remains uncontoured, having thickness T1. Thus, the contoured shape of die 170 allows the die to exhibit a similar appearance to die 150 ( Figures 5A-5D ) the same or similar behavior as shown in .

[0034] Figure 7 is a flow chart of an alternative method 190 for contouring a die 170. During discussion of the method 190, reference may be made to Figure 1 , 2, 5A-5D and 6A-6C.

[0035] At block 192, die 170 is mounted to laminate board 104. At block 194, an operating temperature of die 170 is determined. The operating temperature may be, for example, a normal operating temperature of a production processor having the same design as die 170. At block 196, a test temperature of die 170 is determined. The test temperature may be, for example, substantially similar to the operating temperature (e.g., plus or minus 10° C.) or a substantially different temperature at which die 170 will be tested (e.g., to simulate a startup or overheating condition).

[0036] At block 198, the die 170 is heated to an initial temperature, for example, by operating the die 170 or by using an external heat source (e.g., an oven). The initial temperature can be the same as or similar to the operating temperature of the die 170 (e.g., plus or minus 10°C). The initial temperature can also be the same as or similar to the setting, drying, and / or curing temperature of the former 176 or any adhesive used to bond the former 176 to the laminate 104 at a temperature similar to the operating temperature of the die 170 (e.g., plus or minus 10°C). At block 200, the laminate 104 is adhered to the post 174 and the former 176. Block 200 can be performed, for example, by pouring liquid former 176 between the laminate 104 and the post 174 and allowing the former 176 to set, dry, and / or cure while maintaining the die 170 at or near its operating temperature. For another example, block 200 can be performed by applying an adhesive to the pillars 174, the former 176, and / or the laminate 104 and allowing the adhesive to set, dry, and / or cure while maintaining the die 170 at or near its operating temperature. Thus, block 200 can include heating the former 176 above its setting temperature and / or mixing multiple chemical parts that will dry and / or cure over time.

[0037] At block 202, after the former 176 has solidified, dried, and / or cured, the non-contoured die 170 is contoured at a contouring temperature, e.g., by removing material from its backside so that the contoured die 170 is substantially flat. Even though the die 170 is flattened at the contouring temperature, the die 170 will be substantially flat at the test temperature because the die 170 is being warped by the former 176. At block 204, the backside of the die 170 is polished, e.g., to a mirror finish. At block 206, the mount 172 is separated from the laminate 104 by a chemical (e.g., dissolving), thermal (e.g., heating), and / or mechanical (e.g., cutting) process performed on the former 176. At block 208, the laminate 104 (with the die 170) is then secured in the test fixture 100 by attaching the laminate 104 to the POGO interposer 106. Once secured, the backside of the die 170 is in contact with the cooling plate 118. At block 210, the die 170 is tested by electrically stimulating and operating the die 170 while being viewed through the SIL 116 and cooled by the cooling plate 118.

[0038] The method 190 allows for selective thinning of the die 170 by bringing the die 170 to or near its operating temperature, maintaining the die 170 in its warped shape using the former 176, cooling the die 170 to a profile temperature (e.g., room temperature), planarizing the die 170, and releasing the die 170 and the laminate from the former 176. Thus, the method 190 can profile the die 170 to increase contact and heat transfer between the die 170 and the cooling plate 118.

[0039] In the embodiment shown, die 170 has an operating temperature of 85°C and thus has been selectively thinned to be substantially flat at 85°C. However, if a different operating temperature is desired or anticipated, a different former 176 may be used, for example, one with a different setting, drying, and / or curing temperature or one with a different shape. Thus, die 170 may be substantially flat at the new temperature, which is not possible with known methods, such as a die having a constant thickness (e.g., Figures 2A-2D shown) or simply flattening the die at room temperature (not shown).

[0040] The description of various embodiments of the present disclosure has been presented for illustrative purposes, but is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, practical applications, or improvements over existing technologies in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a computer processor die, the method comprising: determining a first warped shape of a computer processor die at a test temperature; as well as The thickness of the computer processor die is selectively profiled based on the first warped shape at a profile temperature by physically removing material from a surface of the computer processor die so that the surface will be substantially planar at the test temperature.

2. The method according to claim 1, further comprising: determining an operating temperature of the computer processor die; wherein the test temperature is within 10 degrees Celsius of the operating temperature.

3. The method according to claim 1, further comprising: The computer processor die is tested by operating the computer processor die at the test temperature.

4. The method according to claim 3, further comprising: contacting a surface of a computer processor die with a cooling plate; The computer processor die is cooled using the cooling plate during testing of the computer processor die.

5. The method according to claim 1, wherein Determining the first warped shape includes: creating a first virtual model of the computer processor die using finite element analysis; and The first virtual model is selectively contoured to create a second virtual model.

6. The method according to claim 5, further comprising: determining a second warped shape of the second virtual model at the test temperature; as well as The second virtual model is selectively thinned and / or thickened to create a third virtual model such that the virtual surface will be substantially flat at the test temperature.

7. The method according to claim 6, wherein: Selectively contouring a thickness of the computer processor die is performed based on the third virtual model.

8. A method of preparing a computer processor die for testing, the method comprising: determining an operating temperature of the computer processor die; heating the computer processor die to an initial temperature within 10 degrees Celsius of the operating temperature; attaching a forming material to the computer processor die to maintain a shape of the computer processor die near the initial temperature; selectively contouring the thickness of the computer processor die by physically removing material from a surface of the computer processor die so that the surface will be substantially flat at a test temperature, wherein the test temperature is within 10 degrees Celsius of the operating temperature; as well as The computer processor die is separated from the forming material.

9. The method according to claim 8, further comprising: The computer processor die is tested by operating the computer processor die at a test temperature.

10. The method according to claim 9, further comprising: contacting a surface of the computer processor die with a cooling plate; The computer processor die is cooled using the cooling plate during testing of the computer processor die.

11. The method according to claim 8, wherein Attaching the forming material to the computer processor die includes: pouring the forming material between the pillar and the computer processor die; and The forming material is allowed to set, dry and / or solidify.

12. The method according to claim 11, further comprising: The molding material is heated to a temperature equal to or higher than the solidification temperature of the molding material.

13. The method according to claim 12, wherein: The heated forming material heats the computer processor die to the initial temperature.

14. The method of claim 8, wherein: The computer processor die is heated to the initial temperature by operating the computer processor die.

15. The method of claim 8, wherein: Selectively profiling the thickness of the computer processor die by physically removing material from a surface of the computer processor die includes planarizing the surface.

16. The method according to claim 8, wherein Separating the computer processor die from the forming material includes at least one of the group consisting of: heating the forming material and dissolving the forming material.

17. The method according to claim 8, wherein The forming material is wax.

18. A system comprising: A computer processor die formed by the method according to any one of claims 1 to 17; a laminate material connected to said computer processor die; a daughter card electrically connected to the computer processor die to power the computer processor die; a solid immersion lens in contact with a backside of the computer processor die; as well as a cooling plate in contact with a backside of the computer processor die; Wherein, the backside of the computer processor die is substantially flat at an operating temperature of the computer processor die.

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