WO2013050766A1 - Integrated circuit - Google Patents
Integrated circuit Download PDFInfo
- Publication number
- WO2013050766A1 WO2013050766A1 PCT/GB2012/052458 GB2012052458W WO2013050766A1 WO 2013050766 A1 WO2013050766 A1 WO 2013050766A1 GB 2012052458 W GB2012052458 W GB 2012052458W WO 2013050766 A1 WO2013050766 A1 WO 2013050766A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- integrated circuit
- resistor
- trimming
- resistances
- value
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/20—Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
- H01L22/22—Connection or disconnection of sub-entities or redundant parts of a device in response to a measurement
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/22—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming
- H01C17/23—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming by opening or closing resistor geometric tracks of predetermined resistive values, e.g. snapistors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/10—Measuring as part of the manufacturing process
- H01L22/14—Measuring as part of the manufacturing process for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/24—Frequency- independent attenuators
- H03H7/25—Frequency- independent attenuators comprising an element controlled by an electric or magnetic variable
Definitions
- the present invention relates to integrated circuits and methods of manufacturing them, and particularly but not exclusively to integrated circuits that include resistive elements fabricated in silicon and methods of manufacturing them.
- the silicon fabrication process used in the construction of an integrated circuit is such that the absolute value of these resistors formed within the silicon can differ from a target nominal value by a considerable error.
- all resistors on a fabricated wafer are typically scaled from their target value by the same multiplicative error, such that, for example, resistors are n% away from their target value.
- This can cause problems where an application requires a resistance value to be within a tight tolerance band. For example, a specification may require resistance values to be within 10% of their nominal values, but their present production techniques cannot better 15.6%.
- the present applicant has identified the need to improve upon the tolerance with which resistive components can be fabricated.
- an integrated circuit comprising: a plurality of resistors (e.g. formed on a substrate (e.g. wafer) during the same fabrication process); associated with each resistor a plurality n of trimming resistances; and a switch (e.g. switching means) operative to connect a number p, where 0 ⁇ p ⁇ n, of the associated trimming resistances in series with each resistor, whereby the sum of the resistances of the resistor and the trimming resistances form a total resistance value.
- a switch e.g. switching means
- Such an improved integrated circuit is believed to be of use in a variety of fields including but certainly not exclusive to circuitry for handling audio signals.
- the number p of the associated trimming resistances connected in series with each resistor is chosen such that the total resistance value most closely approximates a design resistance value.
- the value of p is the same for each resistor in the integrated circuit.
- the value of p can be the same for all of the resistors because they are all subject to substantially the same manufacturing process, and will therefore deviate from the design resistance value by an error that is proportional to the design resistance value. This greatly simplifies construction of the integrated circuit since every instance of the switch is similarly configured.
- n 1, advantageously, n > 2.
- n 2. In this way, an effective way of controlling resistor tolerance may be provided at minimal cost.
- the values of all of the trimming resistances associated with a particular resistor may be the same. This is most particularly the case where the range of the values of the resistors follows a symmetrical distribution about a mean value.
- the value of each trimming resistance is advantageously approximately 6 ⁇ /( ⁇ + 1), where ⁇ is the standard deviation of the resistance values about the mean.
- ⁇ is the standard deviation of the resistance values about the mean.
- the value of the trimming resistance may be approximately 3 ⁇ .
- an integrated circuit must implement a range of different design resistance values.
- the values of all of the trimming resistances may be of an approximately equal proportion to the value to their associated resistor.
- the switch is typically configured to be programmable once on manufacture of the integrated circuit (e.g. to permanently set the connection of the selected p trimming resistances during manufacture) .
- the switch may include one or more fusible links that can be selectively ruptured to connect the required number of trimming resistances to the resistor.
- the integrated circuit is one of a plurality of integrated circuits on a single substrate each as previously defined, and the switch of each integrated circuit is configured to be activated centrally by a central switch (e.g. by forming a connection from the central switch to each individual switch during manufacture of the integrated circuits.).
- a method of manufacturing an integrated circuit comprising: forming on a substrate (e.g. wafer) a plurality of resistors; forming a plurality n of trimming resistances associated with each resistor; forming a switch that can be caused to connect one or more of the associated trimming resistances in series with each resistor; choosing a value p, where 0 ⁇ p ⁇ n, such that the sum of the resistance of the resistor and p trimming resistances form a total resistance value that most closely approximates a design resistance value; and causing the switch to connect each resistor in series with p of the trimming resistances.
- the value of p is the same for each resistor in the integrated circuit.
- the value p may be chosen by measuring the actual value of a resistor after it has been formed, and setting p to be the number of trimming resistances that, when added to the resistance of the resistor, most closely approximates the design resistance value.
- n 2 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 + (0.05 * (1 +
- the values of all of the trimming resistances associated with a particular resistor are the same.
- the value of the trimming resistance is approximately 6 ⁇ /( ⁇ + 1), where ⁇ is the standard deviation of the values of the resistors values about their mean.
- the values of all of the trimming resistances may be of an approximately equal proportion to the value to their associated resistor.
- the step of causing the switch to connect each resistor in series with p of the trimming resistances involves permanently connecting each resistor with the p trimming resistances.
- the step of causing the switch to connect each resistor in series with p of the trimming resistances may comprise rupture of one or more fusible links.
- the integrated circuit is one of a plurality of integrated circuits on a single substrate each formed as previously defined and the switch of each integrated circuit is caused to connect each resistor in series with p of the trimming resistances by activating a central switch (e.g. by forming a connection from the central switch to each individual switch during manufacture.)
- Figure 1 shows diagrammatically a resistor and a series-connected trimming resistance
- Figure 2 shows diagrammatically a resistor and a switchable series-connected trimming resistance
- Figure 3 is a graph comparing the distribution of resistance values that are obtained in the conventional production of integrated circuits with the distribution of resistance values that are obtained using an arrangement similar to that shown in Figure 2;
- Figure 4 shows diagrammatically a resistor and two switchable series-connected trimming resistances
- Figure 5 is a graph comparing the distribution of resistance values that are obtained in the conventional production of integrated circuits with the distribution of resistance values that are obtained using an arrangement similar to that shown in Figure 4;
- Figure 6 shows diagrammatically a resistor and an arbitrarily large number of switchable series-connected trimming resistances
- Figure 7 is a graph comparing the distribution of resistance values that are obtained in the conventional production of integrated circuits with the distribution of resistance values that are obtained using an arrangement similar to that shown in Figure 6;
- Figure 8 is a graph comparing the distribution of resistance values that are obtained in the conventional production of integrated circuits with the distribution of resistance values that are obtained using an arrangement similar to that shown in Figure 6 when variation in the values of trimming resistances is taken into account;
- Figure 9 shows diagrammatically a resistor ladder where each step in the ladder includes a resistor and two switchable series-connected trimming resistances;
- Figure 1 1 shows the statistics of 1000 embodiments of response characteristics in an integrated circuit with all resistors subject to a Gaussian distribution at ⁇ 5.2% tolerance.
- a resistor R implemented in silicon as part of an integrated circuit.
- the resistor R is connected in series with a trimming resistance Rtrim.
- the total resistance of these two resistors is denoted RT. This is the resistance that will affect operation of the circuit, and should as closely as possible approach a nominal, design value.
- the actual value of this RT in the many integrated circuits will vary with a Gaussian distribution about a mean impedance corresponding to the nominal value.
- the aim is to use series trimming resistance, Rtrim to reduce the width of the distribution of RT.
- trimmer resistor Rtrim will of course have a range of values that following some distribution, which may be correlated with R in silicon implementations. However, by way of explanation consideration will first be given to the case when the trimmer has known, fixed resistance.
- a significantly improved result can be obtained using two trimming resistances Rtrim, l, Rtrim,2, as shown in Figure 4, as before, selection between trimming resistances being made on the basis of the measured value of R.
- the two trimming resistances are of equal value.
- the resistors in an integrated circuit will typically assume a range of different values. For example, a circuit might implement a tapped resistor ladder. Each of these individual values requires trimming to bring their values within the required tolerance range. Despite the absolute values of the resistors being different, the same relative trim amount is required for all resistors for which the proportionality relationship discussed above holds true (that is, all in a wafer or a manufacturing lot). In terms of the scalar examples presented above, this means that the selection of a particular number p (0 ⁇ p ⁇ n) of the n trim resistor values will be identical for each resistor.
- FIG 9 shows the tapped resistor ladders as linked potentiometers - that is, each resistor in the ladder corresponds to a specific setting of the potentiometers.
- the existing resistor ladder [R] is at the left hand end of the ladder as shown in Figure 9.
- each of the trimmers must also be m-step so that there are separate trimmer resistors for each step in the ladder.
- These trimmers have step sizes equal to twice the standard deviation in the variation that is expected in the absolute values of each of the steps of [R]. That means they are of order 10% of the magnitude of [R] to where the manufacturing tolerances are as described above.
- All the taps are set by logic contained within the integrated circuit to ensure that the active section of the resistor ladder [R] is trimmed by the appropriate sections of Rtrim, l and Rtrim,2.
- the one-of-three selection at the right-hand end of Figure 9 is controlled by a common wafer-wide setting, reflecting the actual value of resistance scaling on that wafer.
- a wafer that carries multiple circuits that each includes multiple resistor ladders can be corrected by a single setting. Such as setting could be implemented using fusible links or alternative one-time programmable setting means.
- the actual value of the resistance R can be measured directly, the appropriate number of trimmer resistances can be selected to bring the value of the corresponding RT as close as possible to the nominal value.
- the wafer is then configured such that for every resistor, the correct number of trimming resistances are connected in series. This can be done as a one-time irreversible programming step, implemented, for example, by the provision of fusible links within the wafer.
- a wafer that includes resistors with quoted 3 ⁇ tolerance of 15.6% (Gaussian) can be improved to a flat-top distribution of approximately 5% tolerance. The consequence of such a distribution on the resulting control filters is considered below. (Of course, a corresponding improvement will be obtained when the quoted tolerance is greater than or lesser than 15.6%.)
- Figure 1 1 shows the corresponding statistics when the variation in the resistors is reduced to a ⁇ 5.2% tolerance using the arrangement of two trimming resistances described with reference to Figures 8 and 9. It can be seen that there is a significant reduction in the spread shown in Figure 1 1 as compared with Figure 10.
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Computer Hardware Design (AREA)
- Power Engineering (AREA)
- Semiconductor Integrated Circuits (AREA)
- Design And Manufacture Of Integrated Circuits (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1405479.5A GB2512212B (en) | 2011-10-05 | 2012-10-04 | Integrated circuit with plurality of trimming resistances |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GBGB1117167.5A GB201117167D0 (en) | 2011-10-05 | 2011-10-05 | Integrated circuit |
GB1117167.5 | 2011-10-05 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2013050766A1 true WO2013050766A1 (en) | 2013-04-11 |
Family
ID=45035181
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB2012/052458 WO2013050766A1 (en) | 2011-10-05 | 2012-10-04 | Integrated circuit |
Country Status (2)
Country | Link |
---|---|
GB (2) | GB201117167D0 (en) |
WO (1) | WO2013050766A1 (en) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2171270A (en) * | 1985-02-20 | 1986-08-20 | Sgs Microelettronica Spa | Low noise high thermal stability attenuator of the integratable type |
US6803813B1 (en) * | 2003-04-22 | 2004-10-12 | National Semiconductor Corporation | Time constant-based calibration circuit for active filters |
US20080248601A1 (en) * | 2007-02-13 | 2008-10-09 | Akiko Tsukamoto | Method of fusing trimming for semiconductor device |
-
2011
- 2011-10-05 GB GBGB1117167.5A patent/GB201117167D0/en not_active Ceased
-
2012
- 2012-10-04 WO PCT/GB2012/052458 patent/WO2013050766A1/en active Application Filing
- 2012-10-04 GB GB1405479.5A patent/GB2512212B/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2171270A (en) * | 1985-02-20 | 1986-08-20 | Sgs Microelettronica Spa | Low noise high thermal stability attenuator of the integratable type |
US6803813B1 (en) * | 2003-04-22 | 2004-10-12 | National Semiconductor Corporation | Time constant-based calibration circuit for active filters |
US20080248601A1 (en) * | 2007-02-13 | 2008-10-09 | Akiko Tsukamoto | Method of fusing trimming for semiconductor device |
Also Published As
Publication number | Publication date |
---|---|
GB201405479D0 (en) | 2014-05-07 |
GB2512212A (en) | 2014-09-24 |
GB2512212B (en) | 2015-08-05 |
GB201117167D0 (en) | 2011-11-16 |
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