CN101183135A - Method for measuring semiconductor device inside chip thermocontact area - Google Patents

Abstract

The present invention provides a method for measuring a chip heat contact area inside a semiconductor device, which belongs to the field of a semiconductor device. The present invention is mainly used for measuring the heat contact area of the main heat dissipation structure such as the chip or the tube shell of the device, which is of a qualified electrical properties parameter, so a thermal characteristics examination is facilitated. The technical proposal of the present invention is as follows: the differential is conducted to the transient temperature rise curve of the semiconductor device which is made for measuring a main thermal time constant on a heat conduction path; the thermal transmission length L of the section of structure is worked out through the relationship between the thermal time constant and a thermal resistance and a heat capacity; the temperature rise curve is fitted through the calculated thermal time constant, so a temperature rise value and a heat resistance value which are corresponded with the time constant are worked out. The heat contact area of the structure section is worked out through the relationship between the heat resistance and the heat-transfer length and the contact area of the structure. The method is capable of measuring the actual heat conduction length and the heat contact area inside the semiconductor device and has important application value in the detection and quality analysis aspects for semiconductor device product.

Description

A kind of method of measuring semiconductor device inside chip thermocontact area

Technical field

This method is applicable to the production and the application of semiconductor devices, is mainly used in to measure the qualified device of electric property parameter, and the thermocontact area that main heat radiation such as its chip or shell constitutes is beneficial to the thermal characteristics examination.

Background technology

Finished product semiconductor devices after the encapsulation (as semiconductor transistor, semiconductor field, SIC (semiconductor integrated circuit), semiconductor luminotron and laser instrument etc.) mainly contains semi-conductor chip, scolder and shell and forms.See Fig. 1.When device was worked, heat produced from chip, the diffusing environment towards periphery of flow through scolder and shell.Each part that heat is flowed through all has certain thermal resistance and thermal capacitance.When semiconductor devices from applying power, to steady state (SS), active area temperature uphill process curve in time is exactly that the device transient state adds thermal response curve on the chip of record.Because in the distance that heat is flowed through, the contribution difference of the thermal resistance of each several part, thermal capacitance adds on the thermal response curve in transient state, the flex point that can occur rising, even the appearance of step.Especially after time shaft being adopted logarithmic coordinate, more can tell the nuance of uphill process.See Fig. 2.

Summary of the invention

The purpose of this invention is to provide a kind of method of measuring semiconductor device inside chip thermocontact area, can measure the actual heat conduction length and the actual thermocontact area of semiconductor inside chip.There is being important use to be worth aspect the detection of semiconductor devices product and the quality analysis.

Technical scheme of the present invention is described below:

1, the semiconductor devices transient temperature rise curve to measuring carries out differential, obtains on the heat transfer guiding path, main thermal time constant;

2,, obtain the heat transfer length L of this segment structure by the relation of thermal time constant and thermal resistance, thermal capacitance;

3, the thermal time constant by obtaining is carried out match to temperature rise curve, obtains temperature rise value corresponding with thermal time constant and thermal resistance value.

4,, obtain the thermocontact area of this structure division by the heat transfer length of thermal resistance and structure and the relation of contact area.

A kind of method of measuring semiconductor device inside chip thermocontact area provided by the invention is characterized in that, may further comprise the steps:

1) in the process that temperature rises, use following formulate:

$T\left(t\right)=a_1(1-e^{-t/{\mathrm{\τ}}_1})+a_2(1-e^{-t/{\mathrm{\τ}}_2})+........+a_i(1-e^{-t/{\mathrm{\τ}}_i})$

$=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{a}_i(1-e^{-t/{\mathrm{\τ}}_i})---\left(1\right)$

The τ here _iBe in the semiconductor devices, the different piece of flowing through, the material portion of hot time constant that plays a major role; a _iThen be and τ _iCorresponding structure division reaches after the stable state contribution to whole temperature rise;

2) for the transient temperature rise curve of measuring; Horizontal ordinate is the coordinate of taking the logarithm; 2-4 step arranged in the curve,, obtain thermal time constant τ i by to this curve differentiate;

Thermal time constant is to be associated with the thermal resistance and the thermal capacitance of this structure division, and thermal time constant is:

τ＝R _thC (2)

Thermal resistance and thermal capacitance are respectively:

$R_{\mathrm{th}}=\frac{L}{\mathrm{kS}},C=C_p\mathrm{\ρLS}---\left(3\right)$

Wherein L is the heat transfer length of structure, and S is a thermocontact area, and k is a thermal conductivity, C _pBe specific heat, ρ is a density,

Formula (3) substitution (2) obtains length L:

$L=\sqrt{\frac{\mathrm{\τ}\×k}{C_p\×\mathrm{\ρ}}}---\left(4\right)$

3) measure the heat transfer length L that thermal time constant τ obtains device;

4) the thermal time constant τ i by measuring carries out match according to formula (1), obtains the temperature rise a of counter structure part separately _i

a _i＝P×R _thi

$R_{\mathrm{thi}}=\frac{a_i}{P}=\frac{L_i}{k_i{S}_i}$

$S_i=\frac{L_i\×P}{k_i\×a_i}=\sqrt{\frac{{\mathrm{\τ}}_i\×k_i}{C_{\mathrm{pi}}\×{\mathrm{\ρ}}_i}}\×\frac{P}{k_i\×a_i}$

Wherein the thermal power that applies of device is P, and all the other parameter physical significances as above;

By the measurement and the match of above-mentioned thermal time constant, obtain the thermocontact area S of counter structure part separately.

Inventive point of the present invention place:

1, the thermal time constant τ by measuring with thermal resistance, thermal capacitance relation, measures its heat conduction length.

2, the thermal time constant τ by measuring to the temperature rise curve match, measures the temperature rise value corresponding with timeconstant, by the power P that applies, draws the thermocontact area that device constitutes major part respectively.

3, the size as fruit chip or scolder is regular, and is long-pending consistent as top and bottom, measurement be exactly thermocontact area, if not rule, area is inconsistent up and down, the result of measurement can be considered as equivalent area.

This method by the Measurement and analysis to semiconductor devices transient temperature rise process, can be measured the actual heat conduction length and the thermocontact area of semiconductor inside chip.There is being important use to be worth aspect the detection of semiconductor devices product and the quality analysis.

Description of drawings

Fig. 1 typical semiconductor device vertical stratification a: synoptic diagram; B: thermal resistance thermal capacitance network

1-semi-conductor chip, 2-scolder among the figure, 3-shell, C ₁-chip and scolder thermal capacitance; C ₂-shell thermal capacitance, R _TH1-chip and scolder thermal resistance, R _TH2-shell thermal resistance;

The measurement and the fitting result thereof of Fig. 2 transient temperature rise curve

The differential result of Fig. 3 transient temperature rise curve

Fig. 4 finds the solution the temperature rise value of different thermal time constant correspondences by match

Embodiment

In the process that general temperature rises, can use following formulate:

$T\left(t\right)=a_1(1-e^{-t/{\mathrm{\τ}}_1})+a_2(1-e^{-t/{\mathrm{\τ}}_2})+........+a_i(1-e^{-t/{\mathrm{\τ}}_i})$

$=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{a}_i(1-e^{-t/{\mathrm{\τ}}_i})---\left(1\right)$

The τ here _iBe in the semiconductor devices, the different piece of flowing through, the material portion of hot time constant that plays a major role.a _iThen be and τ _iCorresponding structure division reaches after the stable state contribution to whole temperature rise.

In the general semiconductor devices commonly used, the structure thermal time constant that plays a major role is mainly between 2-4 the parameter.Fig. 2 is the GaAs MESFET transient temperature rise curve actual measurement example of a measurement.Horizontal ordinate is the coordinate of taking the logarithm.Two steps appear in the curve, corresponding two thermal time constants.By to this curve differentiate, obtain this two thermal time constant τ 1, τ 2.See Fig. 3.

Thermal time constant is to be associated with the thermal resistance and the thermal capacitance of this structure division.From the b of Fig. 1 as seen, time constant is:

τ＝R _thC (2)

For the size of rule, as Fig. 1 a, thermal resistance and thermal capacitance are respectively:

$R_{\mathrm{th}}=\frac{L}{\mathrm{kS}},C=C_p\mathrm{\ρLS}---\left(3\right)$

L is the heat conduction length of structure, and S is an area, and k is a thermal conductivity, C _pBe specific heat, ρ is a density, brings 2 into and can obtain the heat conduction length L:

$L=\sqrt{\frac{\mathrm{\τ}\×k}{C_p\×\mathrm{\ρ}}}---\left(4\right)$

By measurement, can obtain the heat conduction length L of device to thermal time constant τ.

By τ 1, the τ 2 that measures, adopt the form of (1), carry out match, obtain separately temperature rise a1, a2.See Fig. 4.

If the thermal power that device applies is P, temperature rise

a＝P×R _th

$R_{\mathrm{th}}=\frac{a}{P}=\frac{L}{\mathrm{kS}}$

$S=\frac{L\×P}{k\×a}=\sqrt{\frac{\mathrm{\τ}\×k}{C_p\×\mathrm{\ρ}}}\×\frac{P}{k\×a}$

By the measurement and the match of above-mentioned thermal time constant, can obtain the thermocontact area S of chip.

For the GaAs MESFET structure that Fig. 1 provides, the transient thermal resistance of measurement (temperature rise) curve is Fig. 2.Two obvious steps are arranged, corresponding respectively chip and solder layer, and base on the curve.

To this curve differential, Fig. 3, peak of curve time corresponding position is exactly a thermal time constant.

For ground floor: material is GaAs

τ=543 μ s, P=0.96W, temperature rise a1=6.39 ℃, R _TH1=6.66 ℃/W, k=54W/m ℃, C _p=325J/Kg ℃, ρ=5370Kg/m ³

Get by formula: L=129 μ m, S=0.36mm ²

For the second layer: material is a copper

τ=309365 μ s, P=0.96W, temperature rise a2=3.24 ℃, R _TH2=3.38 ℃/W, k=392W/m ℃, C _p=390J/Kg ℃, ρ=8920Kg/m ³

Get by formula: L=5.90mm, S=5.30mm ²

By analysis, can obtain the each several part heat conduction length and the thermocontact area of device to these data.Which kind of reason is the thermal resistance of judging device be mainly derived from.When particularly a large amount of same model devices being compared, can filter out the difference between each device.

Claims (1)

1. a method of measuring semiconductor device inside chip thermocontact area is characterized in that, may further comprise the steps:

1) in the process that temperature rises, use following formulate:

$T\left(t\right)=a_1(1-e^{-t/{\mathrm{\τ}}_1})+a_2(1-e^{-t/{\mathrm{\τ}}_2})+........+a_i(1-e^{-t/{\mathrm{\τ}}_i})$

$=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{a}_i(1-e^{-t/{\mathrm{\τ}}_i})---\left(1\right)$

The τ here _iBe in the semiconductor devices, the heat different piece of flowing through, the material portion of hot time constant that plays a major role; a _iThen be and τ _iCorresponding structure division reaches after the stable state contribution to whole temperature rise;

2) for the transient temperature rise curve of measuring; Horizontal ordinate is the coordinate of taking the logarithm; 2-4 step arranged in the curve,, obtain thermal time constant τ i by to this curve differentiate;

Thermal time constant is to be associated with the thermal resistance and the thermal capacitance of this structure division, and thermal time constant is:

τ＝R _thC (2)

Thermal resistance and thermal capacitance are respectively:

$R_{\mathrm{th}}=\frac{L}{\mathrm{kS}},C=C_p\mathrm{\ρLS}---\left(3\right)$

Wherein L is the heat transfer length of structure, and S is a thermocontact area, and k is a thermal conductivity, C _pBe specific heat, ρ is a density,

Formula (3) substitution (2) obtains length L:

$L=\sqrt{\frac{\mathrm{\τ}\×k}{C_p\×\mathrm{\ρ}}}---\left(4\right)$

3) measure the heat transfer that thermal time constant τ obtains device and lead length L;

4) the thermal time constant τ i by measuring carries out match according to formula (1), obtains the temperature rise a of counter structure part separately _i

a _i＝P×R _thi

$R_{\mathrm{thi}}=\frac{a_i}{P}=\frac{L_i}{k_i{S}_i}$

$S_i=\frac{L_i\×P}{k_i\×a_i}=\sqrt{\frac{{\mathrm{\τ}}_i\×k_i}{C_{\mathrm{pi}}\×{\mathrm{\ρ}}_i}}\×\frac{P}{k_i\×a_i}$

Wherein the thermal power that applies of device is P, and all the other parameter physical significances as above;

By the measurement and the match of above-mentioned thermal time constant, obtain the thermocontact area S of counter structure part separately.

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