WO2018169107A1

WO2018169107A1 - Fingerprint recognition sensor and system for improving sensing offset

Info

Publication number: WO2018169107A1
Application number: PCT/KR2017/002872
Authority: WO
Inventors: 전용원; 전창원
Original assignee: 전용원; 주식회사 서키드; 전창원
Priority date: 2017-03-17
Filing date: 2017-03-17
Publication date: 2018-09-20

Abstract

A fingerprint recognition sensor and system for improving a sensing offset is disclosed. The fingerprint recognition sensor of the present invention comprises: a fingerprint terminal; a sensing electrode connected to a sensing node; a protective capacitor electrically connected at one terminal thereof to the sensing electrode and having a protective electrode formed at the other terminal thereof; a sensing pre-charge block operated to pre-charge the sensing node to the voltage of a first pre-charge reference signal; and a sensing readout block for sensing the voltage level of the sensing node so as to generate sensing data. The sensing readout block comprises: a sensing selection switch for connecting the sensing node to a driving node in response to a sensing control signal; a sensing driving unit for sensing the difference between the voltage level of the driving node and an amplification reference voltage so as to generate sensing data; and a compensation unit connected to the driving node and operated to compensate for the effects of parasitic capacitance occurring at the sensing node when the sensing driving unit performs a sensing operation. According to the fingerprint recognition sensor of the present invention, the effects of parasitic capacitance on the sensing electrode is alleviated, so that a sensing offset is reduced, and thus a high-quality fingerprint pattern can be ensured.

Description

Fingerprint Sensors and Systems Improve Sensing Offset

The present invention relates to a fingerprint sensor, and more particularly, to a fingerprint sensor and a system for improving a sensing offset generated when a fingerprint is sensed.

In general, as the information age has made it easier to collect and process desired information, serious problems have arisen where important personal information is easily stolen or destroyed by others. In addition, the development of electronic commerce and the use of mobile electronic devices have highlighted the necessity of restricting access to confidential and personal data. As an alternative to the conventional PIN (Personal Identification Number) or password input and token-based recognition methods such as resident registration card and driver's license, fingerprint recognition method is widely used.

The fingerprint sensor that realizes the fingerprint recognition method may be classified into an optical type, a capacitive type, a thermal type, a resistive type, or an ultrasonic type according to a fingerprint detection method. have.

The capacitive fingerprint recognition sensor recognizes a fingerprint by detecting a difference in the amount of charge stored in the sensing capacitor according to a portion of a finger to be contacted. In the capacitive fingerprint recognition sensor, in order to secure a good fingerprint pattern, it is necessary to reduce the so-called 'sensing offset' according to the parasitic capacitor generated at the sensing electrode forming one terminal of the sensing capacitor. very important.

An object of the present invention is to provide a fingerprint recognition sensor and system for reducing the sensing offset according to the parasitic capacitance of the sensing electrode generated when the fingerprint is sensed.

One aspect of the present invention for achieving the above object relates to a fingerprint sensor. In the fingerprint recognition sensor of the present invention, there is provided a fingerprint recognition sensor comprising: a fingerprint terminal capable of contacting a finger; A sensing electrode connected to a sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger in contact with the fingerprint terminal; One terminal is electrically connected to the sensing electrode, the other terminal is a protective capacitor consisting of a protective electrode, the protective electrode is the protective capacitor for receiving a protective drive signal; A sensing precharge block driven to precharge the sensing node to a voltage of a first precharge reference signal in response to activation of a precharge control signal; And a sensing read block configured to generate the sensing data by sensing the voltage level of the sensing node. The sensing read block may include a sensing select switch configured to connect the sensing node to a driving node in response to a sensing control signal; A sensing driver configured to sense a difference in voltage level of the driving node with respect to an amplification reference voltage to generate sensing data; And a compensation unit connected to the driving node and driven to compensate for the influence of parasitic capacitance generated in the sensing node during the sensing operation of the sensing driver.

One aspect of the present invention for achieving the above object relates to a fingerprint recognition system having a plurality of pixels and a sensing read block. Each of the plurality of pixels may include a fingerprint terminal capable of contacting a finger; A sensing electrode connected to a sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger in contact with the fingerprint terminal; One terminal is electrically connected to the sensing electrode, the other terminal is a protective capacitor consisting of a protective electrode, the protective electrode is the protective capacitor for receiving a protective drive signal; And a sensing precharge block driven to precharge the sensing node to a voltage of a first precharge reference signal in response to a precharge control signal. The sensing read block includes a sensing read block that senses a voltage level of the sensing node of the selected pixel to generate sensing data during sensing driving. The sensing electrode and the protective electrode of at least some of the pixels adjacent to the selected pixel are controlled at the same voltage as the sensing electrode and the protective electrode of the selected pixel during the sensing driving.

In the fingerprint recognition sensor of the present invention, the compensation unit is driven to cancel the parasitic capacitance generated in the sensing electrode forming one terminal of the sensing capacitor. Therefore, according to the fingerprint recognition sensor of the present invention, the sensing offset can be relaxed in the parasitic capacitance of the sensing electrode to ensure a good fingerprint pattern.

A brief description of each drawing used in the present invention is provided.

1 is a diagram conceptually illustrating a fingerprint recognition sensor according to an exemplary embodiment of the present invention.

2 and 3 are timing diagrams for describing an operation of the fingerprint recognition sensor of FIG. 1.

4 is a diagram illustrating an example of the feedback capacitor means of FIG. 1.

FIG. 5 is a diagram illustrating an example of compensation power storage means of the compensation unit of FIG. 1.

6 is a cross-sectional view illustrating a formation form of the sensing electrode and the protective electrode of FIG. 1, and FIG. 7 is a layout view of the sensing electrode and the protective electrode of FIG. 1.

FIG. 8 is a diagram for explaining that factors inducing a 'sensing offset' may be injected from neighboring pixels when sensing a selected pixel.

9 is a diagram illustrating an example in which the first modified feedback capacitor means and the second modified feedback capacitor means are applied in the fingerprint recognition sensor of FIG. 1.

FIG. 10 is a detailed illustration of the first modified feedback capacitor means of FIG. 9 with the relevant components.

FIG. 11 is a detailed illustration of the second modified feedback capacitor means of FIG. 9 with the relevant components.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed subject matter is thorough and complete, and that the scope of the invention to those skilled in the art will fully convey.

In addition, in understanding each drawing, it should be noted that the same member is shown with the same reference numeral as much as possible. Incidentally, detailed descriptions of well-known functions and configurations that are determined to unnecessarily obscure the subject matter of the present invention are omitted.

Meanwhile, in the drawings, thicknesses are enlarged in order to clearly express various layers. Although described from an observer's point of view when referring to the drawings as a whole, when a part such as a layer is "on top" of another part, this includes not only the case where the other part is "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, it means that there is no other part in the middle.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram conceptually illustrating a fingerprint recognition sensor according to an exemplary embodiment of the present invention. 2 and 3 are timing diagrams for describing an operation of the fingerprint recognition sensor of FIG. 1.

Sensing driving of the fingerprint recognition sensor of the present invention is performed through a signal sensing operation P1 (see FIG. 2) and a reference sensing operation P2 (see FIG. 3) distinguished from each other. The signal sensing operation P1 may be divided into a signal precharge process (P11 of FIG. 2) and a signal sensing process (P12 of FIG. 2), and the reference sensing operation P2 may be a reference precharge process. 3 may be divided into a reference sensing process (P22 of FIG. 3).

In the present specification, the signal precharge process (P11 of FIG. 2) and the reference precharge process (P21 of FIG. 3) may be collectively referred to as 'precharge process', and the signal sensing process (of FIG. 2). P12) and the reference sensing process (P22 of FIG. 3) may be collectively referred to as a 'sensing process'.

Referring to FIG. 1 along with FIGS. 2 and 3, the fingerprint recognition sensor of the present invention includes a fingerprint stage (STF), a sensing electrode (ELDT), a protective capacitor (CPDR), a sensing precharge block (BKSNPR), and a sensing read block. (BKSNDR).

The fingerprint terminal STF may contact the finger FNG. The sensing electrode ELDT is electrically connected to the sensing node NSEN.

When the finger FNG contacts the fingerprint terminal STF, the sensing electrode ELDT and the finger FNG serve as one terminal and the other terminal of the virtual sensing capacitor CPDT, respectively. In addition, the finger FNG is grounded through the user's body.

In this case, the amount of charge stored in the sensing capacitor CPDT depends on the degree of contact of the finger FNG, that is, the portion of the finger FNG to be contacted. That is, when the ridges of the fingers FNG are in contact with each other, the amount of charge stored in the sensing capacitor CPDT increases as compared with the case where the valleys of the fingers FNG are in contact with each other. In the fingerprint recognition sensor of the present invention, the pattern of the fingerprint is recognized by confirming the amount of charge stored in the sensing capacitor CPDT.

One terminal of the protection capacitor CPDR is electrically connected to the sensing electrode ELDT, and the other terminal of the protection capacitor CPDR is formed of the protection electrode ELIN. The protection electrode ELIN applies a protection driving signal XDRDT.

In the fingerprint recognition sensor of the present invention, the protection electrode ELIN, which is the other terminal of the protection capacitor CPDR, serves to block unintentional charge into the sensing electrode ELDT.

The formation of the sensing electrode ELDT and the protective electrode ELIN is described in detail later.

In the sensing operation of the fingerprint recognition sensor of the present invention, the voltage level of the protective driving signal XDRDT applied to the protective electrode ELIN is controlled to the same level as the sensing electrode ELDT. Therefore, the amount of charge stored in the protection capacitor CPDR is '0'.

The sensing precharge block BKSNPR is driven to precharge the sensing node NSEN to the voltage of the first precharge reference signal XPRE1 in the precharge processes P11 and P21.

In the present exemplary embodiment, the first precharge reference signal XPRE1 has an upper driving voltage VHG in the signal sensing operation P1 and a lower driving voltage VLW in the reference sensing operation P2. At this time, the upper driving voltage VHG and the lower driving voltage VLW are more than the ground voltage VSS and less than the power supply voltage VDD. The upper driving voltage VHG is higher than the lower driving voltage VLW.

Preferably, the sensing precharge block BKSNPR includes a precharge switch SWPR controlled by a precharge control signal XPCON.

In this case, the precharge switch SWPR is turned on in the precharge processes P11 and P21 and is turned off in the sensing processes P12 and P22.

The sensing read block BKSNDR senses the voltage level of the sensing node NSEN in order to check the degree of contact of the finger FNG with the fingerprint terminal STF, that is, the part of the finger FNG that is in contact with the fingerprint terminal STF. Generate the sensing data DSEN.

In this case, the sensing data DSEN means a difference between voltage levels of the signal data SDA and the reference data RDA. Here, the signal data SDA is generated in the signal sensing operation P1, and the reference data RDA is generated in the reference sensing operation P2.

In detail, the sensing read block BKSNDR includes a sensing selection switch SWST, a sensing driver 100, and a compensator 200.

The sensing select switch SWST is turned on in response to the sensing control signal XSCON in the sensing processes P12 and P22 and is driven to connect the sensing node NSEN to the driving node NDRV. The sensing selection switch SWST is turned off in the precharge processes P11 and P21.

The sensing driver 100 senses a voltage level of the driving node NDRV to generate sensing data DSEN. That is, the sensing driver 100 generates the signal data SDA by sensing the voltage level of the driving node NDRV with respect to the amplification reference voltage VRF in the signal sensing process P12, and generates a reference sensing process ( In operation P22, the voltage level of the driving node NDRV with respect to the amplification reference voltage VRF is sensed to generate reference data RDA.

Preferably, the amplification reference voltage VRF is higher than the ground voltage VSS and lower than the power supply voltage VDD.

More specifically, the sensing driver 100 includes a driving amplifier 110, a reset switch 120, a feedback capacitor means MSCP, and a sampling holding means 140.

The driving amplifier 110 inverts and amplifies the voltage of the driving node NDRV by comparing with the amplifying reference voltage VRF. Here, the amplification reference voltage VRF preferably has a level lower than or equal to the lower driving voltage VLW.

In this case, the driving amplifier 110 generates the signal data SDA in the signal sensing process P12 and is held by the sampling holding means 140. In addition, the driving amplifier 110 generates the reference data RDA in the reference sensing process P22 and is held by the sampling and holding means 140.

The reset switch 120 electrically connects the output node N111 of the driving amplifier 110 with the driving node NDRV in response to the reset signal RST. Here, the reset switch 120 is turned on in the precharge processes P11 and P21 and is turned off before the sensing processes P12 and P22 are started.

Accordingly, in the precharge processes P11 and P21, both the output node N111 and the driving node NDRV of the driving amplifier 110 are controlled to the same level of the amplification reference voltage VRF.

The feedback capacitor means MSCP couples the drive node NDRV to the output node N111 of the drive amplifier. Accordingly, the driving node NDRV is restored to the amplification reference voltage VRF even after sensing is performed in the sensing processes P12 and P22.

On the other hand, in the present embodiment, the gain ratio Ga of the driving amplifier 110 is equal to (Equation 1).

(Equation 1)

Ga =-(Ca / Cg)

Here, Ca is the capacitance of the sensing capacitor (CPDT), Cg is the capacitance of the capacitor (in the present specification, 'drive') formed between the driving node (NDRV), which is an input node of the driving amplifier 110 and the output node in the sensing process. Capacitance ').

Preferably, the feedback capacitor means MSCP has a capacitance that is varied by a capacitance control signal XCAP. In this case, the gain of the driving amplifier 110 may be appropriately controlled. For reference, in the present embodiment, it is difficult to adjust the capacitance Ca of the sensing capacitor CPDT.

4 is a diagram illustrating an example of a feedback capacitor means MSCP of FIG. 1.

Referring to FIG. 4, the feedback capacitor means MSCP includes a first driving feedback capacitor 131, a second driving feedback capacitor 133, and a driving feedback switch 135.

One side of the first driving feedback capacitor 131 is connected to the driving node NDRV, and the other side of the first driving feedback capacitor 131 is connected to the output node N111 of the driving amplifier 110. One side of the second driving feedback capacitor 133 is connected to the driving node NDRV.

The driving feedback switch 135 is driven to connect the other side of the second driving feedback capacitor 133 to the output node N111 of the driving amplifier in response to the activation of the capacitance control signal XCAP.

According to the feedback capacitor means MSCP having the configuration of FIG. 4, the driving capacitance Cg is varied according to whether the capacitance control signal XCAP is activated, and ultimately, the gain ratio of the driving amplifier 110 is increased. Ga) is controlled.

Referring back to FIG. 1, the sampling holding means 140 generates the sensing data DSEN by sampling and holding the voltage of the output node N111 of the driving amplifier 110. That is, in the signal sensing process P12, the sampling holding means 140 samples and holds the signal data SDA provided through the output node N111 of the driving amplifier 110. In the reference sensing process P22, the sampling holding means 140 samples and holds the reference data RDA provided through the output node N111 of the driving amplifier 110.

In this case, the sensing data DSEN is a value of a voltage difference between the signal data SDA and the reference data RDA.

In the fingerprint recognition sensor of FIG. 1, the gain ratio of the driving amplifier 110 is ideally determined by a ratio of the capacitance value of the sensing capacitor CPDT and the capacitance value of the feedback capacitor means MSCP.

However, an unintentional parasitic capacitor CPPD may be generated in the sensing node NSEN. The parasitic capacitor CPPD may cause a 'sensing offset' when sensing the fingerprint sensor.

In order to alleviate the influence of the parasitic capacitor CPPD, the sensing read block BKSNDR includes the compensation unit 200 in the fingerprint recognition sensor of the present invention.

The compensator 200 is connected to the driving node NDRV and is driven to compensate for the influence of the parasitic capacitor CPPD generated in the sensing node NSEN.

In detail, the compensator 200 includes a compensation power storage means 210, a first compensation switch 230, and a second compensation switch 250.

The compensation power storage means 210 includes a compensation capacitor CPSA, and the compensation capacitor CPSA has a capacitance value corresponding to the capacitance value of the parasitic capacitor CPPD. Preferably, the capacitance value of the compensation capacitor CPSA is equal to the capacitance value of the parasitic capacitor CPPD.

The first compensation switch 230 is driven to electrically connect the spare node NPRE to the second precharge reference signal XPRE2 in response to the activation of the precharge control signal XPCON.

In the present exemplary embodiment, the second precharge reference signal XPRE2 has a lower driving voltage VLW in the signal sensing operation P1 and an upper driving voltage VHG in the reference sensing operation P2.

The second compensation switch 250 is driven to electrically connect the spare node NPRE to the driving node NDRV in response to the activation of the sensing control signal XSCON.

Subsequently, the compensation power storage means 210 of the compensation unit 200 of FIG. 1 will be described in more detail.

FIG. 5 is a diagram illustrating an example of the compensation power storage unit 210 of the compensation unit 200 of FIG. 1. Referring to FIG. 5, the compensation power storage unit 210 includes at least one subcapacitor, preferably a plurality of subcapacitors CPSB <1> and CPSB <2>.

For reference, in FIG. 5, for the sake of simplicity, only two subcapacitors are shown, but it is apparent to those skilled in the art that the compensation power storage means 210 may include two or more subcapacitors.

One terminal of the plurality of subcapacitors CPSB <1> and CPSB <2> is electrically connected to the spare node NPRE.

The plurality of subcapacitors CPSB <1> and CPSB <2> are non-exclusively selected in response to respective selection signals SEL <1> and SEL <2>.

At this time, the other terminal of the non-selected sub-capacitor among the plurality of sub-capacitors CPSB <1> and CPSB <2> has the precharge for which the precharge control signal XPCON is activated with “H”. In steps P11 and P21, the voltage is controlled to the voltage of the second precharge reference signal XPRE2.

Here, in the precharge processes P11 and P21 in which the precharge control signal XPCON is activated to “H”, the voltage level of the spare node NPRE is the second precharge reference signal XPRE2. ) Is the voltage.

In addition, the other terminal of the non-selected sub-capacitors among the plurality of sub-capacitors CPSB <1> and CPSB <2> may include the sensing process P12 in which the sensing control signal XSCON is activated with “H”. At P22, the amplification reference voltage VRF is controlled.

Here, in the sensing processes P12 and P22 in which the sensing control signal XSCON is activated with “H”, the voltage level of the spare node NPRE is the amplification reference voltage VRF.

Accordingly, the amount of charge stored in the non-selected sub capacitor among the plurality of sub capacitors CPSB <1> and CPSB <2> is '0'.

The other terminal of the subcapacitor selected from the plurality of subcapacitors CPSB <1> and CPSB <2> is controlled by a capacitor reference voltage VRC.

Preferably, the capacitor reference voltage VRC has a level equal to or higher than the lowest level voltage used to implement the fingerprint recognition sensor of the present invention.

As a result, subcapacitors selected from the plurality of subcapacitors CPSB <1> and CPSB <2> are connected in parallel between the spare node NPRE and the capacitor reference voltage VRC.

That is, the capacitance value of the compensation capacitor CPSA is the sum of the capacitance values of the subcapacitors selected from the plurality of subcapacitors CPSB <1> and CPSB <2>.

In other words, the capacitance value of the compensation capacitor CPSA may be adjusted by selection of the plurality of subcapacitors CPSB <1> and CPSB <2>.

Subsequently, the amount of charge that affects the sensing data DSEN will be described when sensing the fingerprint recognition sensor of the present invention.

As described above, sensing of the fingerprint recognition sensor of the present invention is performed through a signal sensing operation P1 (see FIG. 2) and a reference sensing operation P2 (see FIG. 3) which are distinguished from each other. The signal sensing operation P1 may be divided into a signal precharge process P11 and a signal sensing process P12. The reference sensing operation P2 may be a reference precharge process P21 and a reference sensing method. Process (P22).

First, the net charge amount Qsig affecting the value of the signal data SDA provided to the driving amplifier 110 in the signal sensing operation P1 will be described.

First, the charging amount of each capacitor in the signal precharge process P11 is shown in Table 1 below.

캐패시터(캐패시턴스)Capacitor (Capacitance)	충전량Charge
CPDT(Ca)CPDT (Ca)	VHGCaVHG Ca
CPPD(Cb)CPPD (Cb)	VHGCbVHG Cb
CPDR(Cc)CPDR (Cc)	0Cc0 Cc
CPSA(Cd)CPSA (Cd)	(VLW-VRC)Cd(VLW-VRC) Cd

That is, the total charge amount Qsp in the signal precharge process P11 is equal to (Equation 2).

(Equation 2)

Qsp = VHG * Ca + VHG * Cb + (VLW-VRC) * Cd

In addition, the charging amount of each capacitor in the signal sensing process P12 is shown in Table 2 below.

캐패시터(캐패시턴스)Capacitor (Capacitance)	충전량Charge
CPDT(Ca)CPDT (Ca)	VRFCaVRF Ca
CPPD(Cb)CPPD (Cb)	VRFCbVRF Cb
CPDR(Cc)CPDR (Cc)	0Cc0 Cc
CPSA(Cd)CPSA (Cd)	(VRF-VRC)Cd(VRF-VRC) Cd

That is, in the signal sensing process P12, the total charge amount Qss is equal to (Equation 3).

(Equation 3)

Qss = VRF * Ca + VRF * Cb + (VRF-VRC) * Cd

Therefore, the net charge amount Qsig affecting the value of the signal data SDA provided to the driving amplifier 110 in the signal sensing operation P1 is equal to (Equation 4).

(Equation 4)

Qsig = Qsp-Qss

= (VHG-VRF) * Ca + (VHG-VRF) * Cb + (VLW-VRF) * Cd

Next, the net charge amount Qref that affects the value of the reference data RDA provided to the driving amplifier 110 in the reference sensing operation P2 will be described.

First, the charging amount of each capacitor in the reference precharge process P21 is shown in Table 3 below.

캐패시터(캐패시턴스)Capacitor (Capacitance)	충전량Charge
CPDT(Ca)CPDT (Ca)	VLWCaVLW Ca
CPPD(Cb)CPPD (Cb)	VLWCbVLW Cb
CPDR(Cc)CPDR (Cc)	0Cc0 Cc
CPSA(Cd)CPSA (Cd)	(VHG-VRC)Cd(VHG-VRC) Cd

That is, in the reference precharge process P21, the total charge amount Qrp is equal to (Equation 5).

(Equation 5)

Qrp = VLW * Ca + VLW * Cb + (VHG-VRC) * Cd

In addition, the charging amount of each capacitor in the reference sensing process P22 is shown in Table 4 below.

That is, in the reference sensing process P12, the total charge amount Qrs is equal to (Equation 6).

(Equation 6)

Qrs = VRF * Ca + VRF * Cb + (VRF-VRC) * Cd

Therefore, the net charge amount Qref that affects the value of the reference data RDA provided to the driving amplifier 110 in the reference sensing operation P2 is expressed by Equation 7 below.

(Equation 7)

Qref = Qrp-Qrs

= (VLW-VRF) * Ca + (VLW-VRF) * Cb + (VHG-VRF) * Cd

On the other hand, the amount of charge that affects the sensing data DSEN during the operation of the fingerprint recognition sensor of the present invention affects the value of the signal data SDA provided to the driving amplifier 110 in the signal sensing operation P1. Note is a difference between the net charge Qsig and the net charge Qref that affects the value of the reference data RDA provided to the driving amplifier 110 in the reference sensing operation P2.

Therefore, the amount of charge Qsen that affects the sensing data DSEN during the operation of the fingerprint recognition sensor of the present invention is expressed by Equation (8).

(Equation 8)

Qsen = Qsig-Qref

= (VHG-VLW) * Ca + (VHG-VLW) * Cb + (VLW-VHG) * Cd

In this case, when the capacitance value Cd of the compensation capacitor CPSA and the capacitance value Cb of the parasitic capacitor CPPD are the same, the amount of charge Qsen that affects the sensing data DSEN is (math) Equation 9)

(Equation 9)

Qsen = (VHG-VLW) * Ca

That is, in the fingerprint recognition sensor of the present invention, the sensing data DSEN is determined by the capacitance value Ca of the sensing capacitor CPDT, and the influence of the capacitance value Cb of the parasitic capacitor CPPD is excluded. The sensing offset is reduced.

Therefore, according to the fingerprint recognition sensor of the present invention, the sensing sensitivity with respect to the fingerprint pattern is greatly improved, and it is possible to secure a more clear and accurate fingerprint pattern.

In the fingerprint recognition sensor of FIG. 1, preferably, the capacitor reference voltage VRC has the same level as the amplification reference voltage VRF. In this case, since the charge amount stored in the compensation capacitor CPSA becomes '0' in the signal sensing process P12 and the reference sensing process P22, the sensing efficiency of the fingerprint recognition sensor of the present invention is improved.

On the other hand, the compensation capacitor (CPSA) preferably has an externally adjustable capacitance. In this case, it is easy for the compensation capacitor CPSA to have a capacitance value corresponding to (eg, equal to) the capacitance value of the parasitic capacitor CPPD.

In the present embodiment, the data value of the sensing data DSEN depends on the output difference Vdiff of the driving amplifier 110 in the signal sensing operation P1 and the reference sensing operation P2.

At this time, the output difference (Vdiff) of the driving amplifier 110 is expressed by Equation 10.

(Equation 10)

Vdiff = Ga * (VHG-VLW)

=-(Ca / Cg) * (VHG-VLW)

That is, in the fingerprint recognition sensor of the present invention, the sensing data DSEN may have an appropriate data value by controlling the difference between the upper driving voltage VHG and the lower driving voltage VLW and the driving capacitance Cg. .

Subsequently, in the fingerprint recognition sensor of FIG. 1, the form of formation of the sensing electrode ELDT and the protective electrode ELIN is described in detail.

6 is a cross-sectional view illustrating a formation form of the sensing electrode ELDT and the protective electrode ELIN of FIG. 1, and FIG. 7 is a layout diagram of the sensing electrode ELDT and the protective electrode ELIN of FIG. 1. 6 and 7, components directly related to the present invention are shown centrally, and the remaining components are omitted or abbreviated.

6 and 7, the protective electrode ELIN is formed of the first metal layer MET1 formed on the substrate SUB. In this case, as described above, the protective driving signal XDRDT is applied to the protective electrode ELIN formed of the first metal layer MET1.

In FIG. 6, reference numeral 'LMUS' conceptually represents various types of materials including an insulating layer that may be formed between the first metal layer MET1 and the substrate SUB.

The sensing electrode ELDT is formed of a second metal layer MET2 or a third metal layer MET3 stacked on the first metal layer MET1 forming the protective electrode ELIN.

In this case, as described above, the protective driving signal XDRDT is applied to the protective electrode ELIN formed of the first metal layer MET1. In this case, the sensing electrode ELDT formed of the second metal layer MET2 is formed by the protection electrode ELIN, such as a peripheral charge and coupling effect that can be injected into the bottom, such as a 'sensing offset'. Can be protected against factors that can cause.

A protective dielectric layer LPRF of a dielectric material is formed between the second metal layer MET2 forming the sensing electrode ELDT and the first metal layer MET1 forming the protective electrode ELIN.

As a result, a protective capacitor CPDR is formed using the sensing electrode ELDT as one terminal and the protective electrode ELIN as the other terminal.

The fingerprint terminal STF is formed of a surface dielectric layer LSUR of a dielectric material stacked on the second metal layer MET2 forming the sensing electrode ELDT.

In this case, when the finger FNG contacts the fingerprint terminal STF, the sensing electrode ELDT and the finger FNG act as one terminal and the other terminal of the virtual sensing capacitor CPDT, respectively. As shown.

The sensing electrode ELDT formed as described above is covered by the surface dielectric layer LSUR, and thus is not exposed to the outside.

Preferably, the surface dielectric layer LSUR is composed of a first surface dielectric layer LSUR1 and a second surface dielectric layer LSUR2. The first surface dielectric layer LSUR1 is formed by being stacked on the second metal layer MET2 forming the sensing electrode ELDT.

6 and 7, formed on the first surface dielectric layer LSUR1 and penetrating through the first surface dielectric layer LSUR1 and the protective dielectric layer LPRF, the first metal layer MET1 The third metal layer MET3 in contact contact also acts as the protective electrode ELIN.

The second surface dielectric layer LSUR2 is formed by being stacked on the first surface dielectric layer LSUR1 on which the third metal layer MET3 is formed.

In this case, the sensing electrode ELDT formed of the second metal layer MET2 is not only from below but also from offset factors such as peripheral charge and coupling effects that can be injected from the side. Can be protected.

On the other hand, the fingerprint recognition system generally comprises a plurality of fingerprint recognition pixels. The fingerprint recognition pixels may include the sensing electrode ELDT and the protection electrode ELIN of the fingerprint recognition sensor of the present invention.

In this case, as shown in FIG. 8, factors inducing a 'sensing offset' from the surrounding pixels BPIX may be injected during sensing driving of the selected pixel SPIX.

In this case, the sensing electrodes ELDTs and the protection electrodes ELIN of at least some of the adjacent pixels BPIX that are disposed around the selected pixel SPIX are also selected. By controlling to the same voltage as the ELDT and the protective electrode ELIN, the sensing electrode ELDT of the selected pixel SPIX can be more effectively protected from the off-set generating factors.

Meanwhile, in the fingerprint recognition sensor of FIG. 1, the feedback capacitor means MSCP may be modified in various forms.

FIG. 9 is a diagram illustrating an example in which the modified feedback capacitor means is applied in the fingerprint recognition sensor of FIG. 1.

In the fingerprint recognition sensor of FIG. 9, at least one of the first modified feedback capacitor means MSCP1 and the second modified feedback capacitor means MSCP2 is included in place of the feedback capacitor means MSCP of FIG. 1. In this case, the first modified feedback capacitor means MSCP1 is formed between the output node N111 and the sensing node NSEN of the drive amplifier 110, and the first modified feedback capacitor means MSCP1 is a drive amplifier. It is formed between the output node N111 and the spare node NPRE of 110.

FIG. 10 is a detailed illustration of the first modified feedback capacitor means MSCP1 of FIG. 9 with the relevant components.

Referring to FIG. 10, the first modified feedback capacitor means MSCP1 may include a first sensing feedback capacitor 171, a second sensing feedback capacitor 172, a first sensing feedback switch 173, and a second sensing feedback switch. 174, a third sensing feedback switch 175 and a fourth sensing feedback switch 176.

One side of the first sensing feedback capacitor 171 and the second sensing feedback capacitor 172 is connected to the sensing node NSEN.

The first sensing feedback switch 173 electrically connects the other side of the first sensing feedback capacitor 171 and the output node N111 of the driving amplifier 110 in response to the sensing control signal XSCON. Let's do it.

The second sensing feedback switch 174 is in response to the activation of the first capacitance control signal XCAP1, the other side of the first sensing feedback capacitor 171 and the other side of the second sensing feedback capacitor 172. Is electrically connected.

The third sensing feedback switch 175 electrically connects the other side of the first sensing feedback capacitor 171 to the first precharge reference signal XPRE1 in response to the first precharge control signal XPCON. Driven to be connected.

The fourth sensing feedback switch 176 electrically connects the other side of the second sensing feedback capacitor 172 to the protection driving signal XDRDT in response to the deactivation of the first capacitance control signal XCAP1. Driven to connect.

In the first modified feedback capacitor means MSCP1 having the configuration of FIG. 10, when the first capacitance control signal XCAP1 is activated, in the sensing process of activating a sensing control signal XSCON, the first sensing is performed. A feedback capacitor 171 and the second sensing feedback capacitor 172 are formed in parallel with the output node N111 and the sensing node NSEN of the driving amplifier 110.

That is, when the first capacitance control signal XCAP1 is activated, the driving capacitance Cg becomes large.

When the first capacitance control signal XCAP1 is deactivated, the second sensing feedback capacitor 172 and the protection capacitor CPDR are formed in parallel between the sensing node NSEN and the protection driving signal XDRT. do.

That is, when the first capacitance control signal XCAP1 is deactivated, the driving capacitance Cg is reduced, and the second sensing feedback capacitor 172 enhances the action of the protection capacitor CPDR.

FIG. 11 is a view detailing the second modified feedback capacitor means MSCP2 of FIG. 9 with the relevant components.

Referring to FIG. 11, the second modified feedback capacitor means MSCP2 may include a first sensing feedback capacitor 191, a second sensing feedback capacitor 192, a first sensing feedback switch 193, and a second sensing feedback switch. 194, a third sensing feedback switch 195 and a fourth sensing feedback switch 196.

One side of the first sensing feedback capacitor 191 and the second sensing feedback capacitor 194 is connected to the spare node NPRE.

The first sensing feedback switch 193 electrically connects the other side of the first sensing feedback capacitor 191 and the output node N111 of the driving amplifier 110 in response to the sensing control signal XSCON. Let's do it.

The second sensing feedback switch 194 is in response to the activation of the second capacitance control signal XCAP2, the other side of the first sensing feedback capacitor 191 and the other side of the second sensing feedback capacitor 192. Is electrically connected.

The third sensing feedback switch 195 electrically connects the other side of the first sensing feedback capacitor 191 to the first precharge reference signal XPRE1 in response to the first precharge control signal XPCON. Driven to be connected.

The fourth sensing feedback switch 196 electrically connects the other side of the second sensing feedback capacitor 192 to the protection driving signal XDRDT in response to deactivation of the second capacitance control signal XCAP2. Driven to connect.

In the second modified feedback capacitor means MSCP2 having the configuration of FIG. 11, when the second capacitance control signal XCAP2 is activated, in the sensing process of activating a sensing control signal XSCON, the first sensing is performed. A feedback capacitor 191 and the second sensing feedback capacitor 192 are formed in parallel to the output node N111 and the spare node NPRE of the driving amplifier 110.

That is, when the second capacitance control signal XCAP2 is activated, the driving capacitance Cg becomes large.

When the second capacitance control signal XCAP1 is inactivated, the second sensing feedback capacitor 192 and the protection capacitor CPDR are formed in parallel between the spare node NPRE and the protection driving signal XDRT. do.

That is, when the second capacitance control signal XCAP2 is inactivated, the driving capacitance Cg is reduced, and the second sensing feedback capacitor 192 enhances the action of the protection capacitor CPDR.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

For example, it will be apparent to those skilled in the art that various switches may be implemented in various forms such as PMOS transistors, NMOS transistors, transmission gates, and the like.

Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The present invention is applicable to the field of fingerprint recognition.

Claims

In the fingerprint sensor,

Fingerprint stage that can be touched by the finger;

A sensing electrode connected to a sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger in contact with the fingerprint terminal;

One terminal is electrically connected to the sensing electrode, the other terminal is a protective capacitor consisting of a protective electrode, the protective electrode is the protective capacitor for receiving a protective drive signal;

A sensing precharge block driven to precharge the sensing node to a voltage of a first precharge reference signal in response to activation of a precharge control signal; And

A sensing read block configured to sense the voltage level of the sensing node to generate sensing data;

The sensing read block is

A sensing select switch connecting the sensing node to a driving node in response to a sensing control signal;

A sensing driver configured to sense a difference in voltage level of the driving node with respect to an amplification reference voltage to generate sensing data; And

And a compensation unit connected to the driving node, the compensation unit being driven to compensate for the influence of parasitic capacitance generated in the sensing node during the sensing operation of the sensing driver.
The method of claim 1, wherein the compensation unit

Compensation power storage means including a compensation capacitor having a capacitance value corresponding to the parasitic capacitor, the compensation capacitor comprising: at least one sub-capacitor having one terminal electrically connected to the spare node;

A first compensation switch configured to control the voltage of the second precharge reference signal to the spare node in response to activation of the precharge control signal;

And a second compensation switch driven to electrically connect the spare node to the driving node in response to activation of the sensing control signal.
The terminal of claim 2, wherein the other terminal of the at least one subcapacitor is

A fingerprint recognition sensor, which can be controlled with a capacitor reference voltage.
The method of claim 3, wherein the compensation capacitor

A plurality of subcapacitors including the at least one subcapacitor, the plurality of subcapacitors being nonexclusively selected in response to a respective selection signal;

One terminal of each of the plurality of subcapacitors

Is electrically connected to the spare node,

The other terminal of the subcapacitor selected from the plurality of subcapacitors is

And a fingerprint reference sensor controlled to the capacitor reference voltage.
The method of claim 4, wherein the capacitor reference voltage is

And the same level as the amplification reference voltage.
The terminal of claim 4, wherein the other terminal of the sub-capacitor that is not selected among the plurality of sub-capacitors is formed.

In response to the activation of the precharge control signal, controlling the voltage to the second precharge reference signal;

And in response to the activation of the sensing control signal, controlled by the amplification reference voltage.
The method of claim 1, wherein the sensing driver

A driving amplifier inverting and amplifying the voltage of the driving node with the amplifying reference voltage;

A reset switch driven to electrically connect an output node of the drive amplifier to the drive node in response to a reset signal;

Feedback capacitor means for coupling the drive node to an output node of the drive amplifier; And

And sampling holding means for sampling and holding the voltage of an output node of the driving amplifier to generate the sensing data.
The method of claim 1, wherein the feedback capacitor means

And a capacitance varying in response to a capacitance control signal.
According to claim 1,

The protective electrode

It is formed of a first metal layer laminated on the substrate,

The sensing electrode

A second metal layer stacked on the first metal layer forming the protective electrode,

The fingerprint end is

And a surface dielectric layer stacked on the second metal layer forming the sensing electrode.
The method of claim 9, wherein the surface dielectric layer is

A first surface dielectric layer deposited over the second metal layer forming the sensing electrode; And

A second surface dielectric layer laminated over said first surface dielectric layer,

The protective electrode

A third metal layer formed over the first surface dielectric layer and in contact with the first metal layer through the first surface dielectric layer and the protective dielectric layer, wherein the protective dielectric layer is formed between the first metal layer and the second metal layer And a third metal layer.
In the fingerprint sensor,

Fingerprint stage that can be touched by the finger;

A sensing electrode connected to a sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger in contact with the fingerprint terminal;

One terminal is electrically connected to the sensing electrode, the other terminal is a protective capacitor consisting of a protective electrode, the protective electrode is the protective capacitor for receiving a protective drive signal;

A sensing precharge block driven to precharge the sensing node to a voltage of a first precharge reference signal in response to activation of a precharge control signal; And

A sensing read block configured to sense the voltage level of the sensing node to generate sensing data;

The protective electrode

It is formed of a first metal layer laminated on the substrate,

The sensing electrode

A second metal layer stacked on the first metal layer forming the protective electrode,

The fingerprint end is

A surface dielectric layer stacked on the second metal layer forming the sensing electrode,

The surface dielectric layer

A first surface dielectric layer deposited over the second metal layer forming the sensing electrode; And

A second surface dielectric layer laminated over said first surface dielectric layer,

The protective electrode

A third metal layer formed over the first surface dielectric layer and in contact with the first metal layer through the first surface dielectric layer and the protective dielectric layer, wherein the protective dielectric layer is formed between the first metal layer and the second metal layer And a third metal layer.
In the fingerprint recognition system having a plurality of pixels and the sensing read block,

Each of the plurality of pixels

Fingerprint stage that can be touched by the finger;

A sensing electrode connected to a sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger in contact with the fingerprint terminal;

One terminal is electrically connected to the sensing electrode, the other terminal is a protective capacitor consisting of a protective electrode, the protective electrode is the protective capacitor for receiving a protective drive signal; And

A sensing precharge block driven to precharge the sensing node to a voltage of a first precharge reference signal in response to a precharge control signal,

The sensing read block is

And a sensing read block configured to generate sensing data by sensing a voltage level of the sensing node of the selected pixel during sensing driving.

The sensing electrode and the protective electrode of at least some of the pixels adjacent to the selected pixel during the sensing driving are

And the sensing electrode and the protection electrode of the selected pixel are controlled at the same voltage.